# Porting 101



## pepsifreak28

I would like to start a sticky for porting...
I see a lot of people asking questions about porting..
feel free to add to this thread all you fellow modders..

first things first here you got to understand how 2 stroke engines operate just because you know the basics dont mean nothing here is a basic video of a two stroke..


http://www.youtube.com/watch?v=LuCUmQ9FxMU


once you understand the basic idea of it watch the video again..and think about how you can improve its operation..


if you thought by getting air/fuel mixtured burned and out of the engine you guessed right..


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## pepsifreak28

Okies now that you got that down we can move onto some more advanced stuff..

the first thing to porting and engine just the basic "improvements" most mass production engines are cast from molds so you will find casting flaws and such all thoughout the bore/jug removeing them will increase flow a lot.. meaning more air/fuel moveing though the engine more fuel and air yay! we want more air and fuel moveing though the engine.

there are other ways we can improve though so we are going to look into what else can we do to make more air/fuel move though the engine better?
I know lets wideing those openings a little! since we got some extra metal around the openings..


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## pepsifreak28

so now you got your jug from your chainsaw you can see in from the bottom end though the exhaust opening/port and though the intake where the carb flows into it..
looking all around the inside your looking for more ways to get more air/fuel into the engine so lets follow the flow of combustion first thing the engine does is sucks fuel/air in though the carb and into the crankcase..

then into the crankcase where it is forced up though the passageways around the piston and into the combustion area..


then its compressed and ignighted and then out the exhaust pipe...


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## blsnelling

Here ya go. LINK. LINK


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## pepsifreak28

now once you see the flow of things you can begin to improve on somethings removeing those casting flaws and widening some of the ports and allowing more air and fuel to flow though the engine

here is some pics of a ported 2 stroke dirt bike engine up close and personal


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## damifino

*Keep it at beginner level*

You have a good start, keep it going. There is a lot of porting info out there but it goes from beginner to more advanced to quickly for me.


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## pepsifreak28

In this picture you can see the crankcase to combustion chamber transfer ports if you notice they have been filed/ground to improve flow and to a nice edge and widened a little as well doing this will alow more air and fuel to flow easyier into the combustion chamber


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## pepsifreak28

In this picture you can see the exhaust port the circle is more than likely around where it use to be stock
notice the new oval shape its kind of shaped like a folded funnel


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## pepsifreak28

When you start to port your engine the first thing to do is look inside the jug and at all the ports and see how you can improve the flow of air and fuel you should start to notice casting flaws and extra metal here and there
I like to use a locksmith file set on weed eaters and small engines its easyier to get a file in then it is a dremel plus you dont take as much metal off as fast a chainsaw chain file works great too


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## pepsifreak28

The more advanced stuff will come in time the main goal for now is to just improve the flow without going overboard a little improvment will go a long way faster throttle response and better performance overall there is some risk to porting that you should take note off if you take metal from the bottom of the exhaust port to much will allow free porting that means your piston travels to tdc it exposes the exhaust port to the crankcase bad idea that will allow the fuel/air mixture to vent into the exhaust and not into the combustion area though the transfer ports..

also some other risk are DONT GO OVERBOARD! sometimes and it has happened to be before is you grind to much and expose an air leak this happens a lot on the transfer ports if you dont make to big of a hole you can fix it with jb weld or epoxy but we dont wanna go to far so make sure you got the metal on the outside of the jug to grind..


here is anouther risk that often takes place in porting when you widen ports dont forget the rings there your friend  they half to travel over those ports many times
if you go to wide your piston ring can pop out into the port and snag it snap the ring and its not a pretty site ....


there is other risk as allways but when you start to "clean up" the casting flaws and improveing flow you will start to see about how far you can take something dont get greedy with porting a little can improve a lot the exhaust port alone can make a big difference as you noticed with the muffler mods..


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## pepsifreak28

I'm not the best picture drawer so bear with me in this picture you can see the basic idea of the engine the green parts is where the fuel and air is I like to pack as much fuel and air in this area as i can so improveing flow into here is a big improvement i see a lot of weed wackers and some chainsaws that could really improve in the intake area as well as exhaust i notice a lot of small engines that have a very short intake duration (meaning how long the port window is open) and short exhaust duration if you lower the intake port a little(dont go overboard here as you need some closed time)the closed time is the time its pushing the fuel air mixture into the combustion chamber if you didnt have a closed time it would spray fuel out the carb and not into the transfer ports into the combustion chamber when you get into duration and such the main thing is to watch the video at the very top or watch basic 2 stroke operation and think in your head of the rhythm of the engine makes me think of those old hit and miss engines  take that rhythm and go look at your chainsaw engine crank it around a few times by hand and watch how the ports open and close you should see a rhythm now as your watching the ports open and close realtive to the piston travels the faster the ports open and close the more rpm you get or the distance from the intake to the exhaust somewhat like intake exhaust intake exhaust intake exhaust intake exhaust if you have some distance between the ports you will get a rhythm like intake space exhaust intake space exhaust intake space exhaust member there is a little time between the intake and exhaust stroke to allow the fuel to be pushed from the crankcase into the combustion area so rhythm is the duration of the port window and the timeing this is on piston ported engines where the duration really matters thats why on dirt bikes they use reed valves if you really mess up in the intake area you will half to make a reed cage and thats not a bad thing if you was to make a reed cage and put reeds on your saw but im not sure if you would be able to put the plastic parts back on anyways the main thing to reamember is when messing with the intake side of things improveing flow is a good thing but watching the duration as well you got to have that moment where its closed to allow the pistons downward movement to push the air and fuel into the transfer ports into the combustion chamber we wouldnt half to worry about this is we had a reed cage if there is some people in the forum that can make some reed cages for chainsaws i would buy one the reed cage is awesome imo because as soon as that piston starts going down it closes and you get almost the entire downward pressure of the piston to pack all the air and fuel into the combustion area meaning you can open your intake as far as you like allmost anyways back to the piston ported engine so when working on the intake side just reamember there has to be some time in there to allow the piston to push the fuel and air into the transfers into the combustion area so just watch the rhythm of your engine and think of it like a song in your head the best i can decribe it is with a tune


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## pepsifreak28

now the exhaust side the exhaust side is critical in one area the bottom of the port you go to far and you get free porting free porting is when the piston is at tdc it exposes the crankcase to the exhaust bad thing so be careful on the bottom now onto the details the exhaust port can be improved by widening getting all those burnt fuel out better improves things as far as exhaust goes the closer the port goes to tdc you will get a tingy high reving rpm engine with less torque the lower the port is to tdc the more torque you get the reason that is the fuel that is burning is expanding so the longer you hold the expanding gasses the more power you get from it the faster you ignight the fuel and release it out the exhaust pipe the less power you get from the charge so you get higher rpm the faster the fuel explodes and out the pipe the more you hold it in the higher the buzz j/k the higher the torque so in basics...

higher the port is to tdc =higher rpms
the lower the port is to tdc = more torque

note: when i say lower thats not grinding the bottom of the port 

in modern 2 stroke dirt bikes if you ever rode the water cooled insane hell of a ride dirt bikes you will notice when you first start moveing you dont got high reving engine but when you get into the throttle a little you notice a drastic change in the bike it about throws you off like the engine woke up! how that works is what are called power valves its basicly a plate that is on the roof of the exhaust port that drops down on slower take offs and raises as the engine picks up rpms so it drasticly changes the duration and opens up the port to allow the rpms to increase so in a chainsaw if you wanted more torque you would need to add metal to the top of the port.


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## pepsifreak28

one thing to remember is that the engineers made the engine for the job.. you wouldnt want a high rpm engine on a chainsaw and you wouldnt want a high torque engine on a go cart so the engineers made the engine for its purpose I have seen guys that have gotten porting done and they think OHH! high rpms that sounds good so they get the porting done for high rpms but when you get high rpms you almost forget that you need some torque too its all basicly what you wanna do with the engine with chainsaws if you had high rpm would the bar and chain hold the higher rpm? or would it fly off so think about what you want from the engine if you had higher torque would it break the chains? or would it dull it fast take everything into consideration but for you beginners on the forum start with improveing the flow weed wackers in many areas you can find them in the trash some ryobi and stihl weed eaters have a reed cage if you get one of those you can really mod and tinker with it and not worry to much about messing it up beyond it being able to be used as weed wackers or trimmers you can sway with high rpm or high torque and it will still work it dont take much to cut grass.


please let me know if i missed anything blsnelling is a very good advanced porter i mainly wanted to explain the basics 
there is a lot of porting going on in all areas of 2 strokes

you have the rc boaters/aircraft 
dirt bike/four wheeler/carting/snowmobile/jet ski
chainsaw/weedwacker 
almost all of them mod 2 stroke engines 
for different tasks and raceing 

I will try and keep adding to this thread as i find more pictures and websites feel free to add your pictures.


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## mweba

Great thread guys! Have read most of this already but nice having it in one place to reference. One thing I do not see enough of is examples of the tools needed/used to do the detailed work. Myself and others use carbide dremel bits for the ruff work, and various gritt sanding balls for the chamfer and cleanup. Have not yet figured out how to down size my pics or I would post what I use.


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## edisto

This is your post:



tomtrees58 said:


> your rails are blue oil problem or you do not used bar oil we have a bar rail grinder its excellent but we have 35 sthil saws for you by a new bar tom trees



This is your post on crystal meth:



pepsifreak28 said:


> I'm not the best picture drawer so bear with me in this picture you can see the basic idea of the engine the green parts is where the fuel and air is I like to pack as much fuel and air in this area as i can so improveing flow into here is a big improvement i see a lot of weed wackers and some chainsaws that could really improve in the intake area as well as exhaust i notice a lot of small engines that have a very short intake duration (meaning how long the port window is open) and short exhaust duration if you lower the intake port a little(dont go overboard here as you need some closed time)the closed time is the time its pushing the fuel air mixture into the combustion chamber if you didnt have a closed time it would spray fuel out the carb and not into the transfer ports into the combustion chamber when you get into duration and such the main thing is to watch the video at the very top or watch basic 2 stroke operation and think in your head of the rhythm of the engine makes me think of those old hit and miss engines  take that rhythm and go look at your chainsaw engine crank it around a few times by hand and watch how the ports open and close you should see a rhythm now as your watching the ports open and close realtive to the piston travels the faster the ports open and close the more rpm you get or the distance from the intake to the exhaust somewhat like intake exhaust intake exhaust intake exhaust intake exhaust if you have some distance between the ports you will get a rhythm like intake space exhaust intake space exhaust intake space exhaust member there is a little time between the intake and exhaust stroke to allow the fuel to be pushed from the crankcase into the combustion area so rhythm is the duration of the port window and the timeing this is on piston ported engines where the duration really matters thats why on dirt bikes they use reed valves if you really mess up in the intake area you will half to make a reed cage and thats not a bad thing if you was to make a reed cage and put reeds on your saw but im not sure if you would be able to put the plastic parts back on anyways the main thing to reamember is when messing with the intake side of things improveing flow is a good thing but watching the duration as well you got to have that moment where its closed to allow the pistons downward movement to push the air and fuel into the transfer ports into the combustion chamber we wouldnt half to worry about this is we had a reed cage if there is some people in the forum that can make some reed cages for chainsaws i would buy one the reed cage is awesome imo because as soon as that piston starts going down it closes and you get almost the entire downward pressure of the piston to pack all the air and fuel into the combustion area meaning you can open your intake as far as you like allmost anyways back to the piston ported engine so when working on the intake side just reamember there has to be some time in there to allow the piston to push the fuel and air into the transfers into the combustion area so just watch the rhythm of your engine and think of it like a song in your head the best i can decribe it is with a tune



Any questions?


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## Hddnis

edisto said:


> This is your post:
> 
> 
> 
> This is your post on crystal meth:
> 
> 
> 
> Any questions?





This made my day.


Mr. HE


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## Hddnis

pepsifreak, just from skimming through your posts there seems to be a wealth of information. If you could break your posts into sentences and paragraphs it would make that information more accessible and understandable.

Keep up the good work.


Mr. HE


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## Freehand

edisto said:


> This is your post:
> 
> 
> 
> This is your post on crystal meth:
> 
> 
> 
> Any questions?



Say what you will about Tomtree's posts ,however undecipherable ,the man does some uber gnarly tree work.....his pictures are much better

Pepsifreak,don't let these guys run you off.....they're gonna poke atcha but it's par for the course posting here

Addressing your composition....edisto is not far off,run-on sentences are seemingly incoherent and very difficult to follow.

Slow it down a little,break it into sub-topics and bring it mang.....then everyone will be able to appreciate what you have to offer


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## pepsifreak28

*lol*

Sorry about all that I wrote it on a half working laptop in a hurry and I am horrid with writing and explaining things. I do my best  but I am willing to help share knowledge the best I can if you or someone would like to rewrite it ,add to it ,redo the pictures feel free I won't be upset or mad just wanted to help explain things with porting and the do and don'ts let me know if you would like to resize the pictures or make them better sent me a private message and ill edit the post ..


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## TraditionalTool

pepsifreak28 said:


> Sorry about all that I wrote it on a half working laptop in a hurry and I am horrid with writing and explaining things. I do my best  but I am willing to help share knowledge the best I can if you or someone would like to rewrite it ,add to it ,redo the pictures feel free I won't be upset or mad just wanted to help explain things with porting and the do and don'ts let me know if you would like to resize the pictures or make them better sent me a private message and ill edit the post ..


I'm watching and have some Qs, but more so in regard to my specific cylinder, and how to evaluate it.


pepsifreak28 said:


> In this picture you can see the exhaust port the circle is more than likely around where it use to be stock
> notice the new oval shape its kind of shaped like a folded funnel


I have seen others show that shape also, so that is obviously what works. In general is the concept to keep the top and bottom the same and elongate the smashed funnel shape as you show here?

Also, another thing I was wondering is that if you leave the opening top/bottom of the port the same, do you try and hollow/expand it out behind the cylinder also?

Thanks for sharing, I am one of the folks that is wanting to learn, and I appreciate the time you've taken, don't worry about your formatting of the content, the pics are fine, and just try to hit the enter key a couple times now and then, a little white space would help, but don't let that stop you from posting. 

Can you offer some advice on how you would approach this cylinder?

Like how far you would take the funnel shape out to the sides, or any info like that would be helpful. What about the fins on the sides also?

Yes, yes, I know I need to clean it up with muriatic acid...

Intake:






Exhaust:


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## Freehand

pepsifreak28 said:


> I'm not the best picture drawer so bear with me. In this picture you can see the basic idea of the engine: the green parts is where the fuel and air is. I like to pack as much fuel and air in this area as i can so improving flow into here is a big improvement. I see a lot of weed wackers and some chainsaws that could really improve in the intake area as well as exhaust. I notice a lot of small engines that have a very short intake duration (meaning how long the port window is open) and short exhaust duration. If you lower the intake port a little(dont go overboard here as you need some closed time).The closed time is the time its pushing the fuel air mixture into the combustion chamber. If you didnt have a closed time it would spray fuel out the carb and not into the transfer ports and into the combustion chamber. When you get into duration and such the main thing is to watch the video at the very top or watch basic 2 stroke operation and think in your head of the rhythm of the engine, makes me think of those old hit and miss engines. Take that rhythm and go look at your chainsaw engine and crank it around a few times by hand and watch how the ports open and close. You should see a rhythm now as you're watching the ports open and close realtive to how the piston travels. The faster the ports open and close the more rpm you get. The distance from the intake to the exhaust is somewhat like intake exhaust intake exhaust intake exhaust intake exhaust. If you have some distance between the ports you will get a rhythm like intake space exhaust intake space exhaust intake space exhaust. Remember there is a little time between the intake and exhaust stroke to allow the fuel to be pushed from the crankcase into the combustion area, so rhythm is the duration of the port window. And timeing this is on piston ported engines where the duration really matters. Thats why on dirt bikes they use reed valves. If you really mess up in the intake area you will have to make a reed cage, and thats not a bad thing if you was to make a reed cage and put reeds on your saw. But im not sure if you would be able to put the plastic parts back on anyways. The main thing to remember is when messing with the intake side of things improveing flow is a good thing. But watching the duration as well you got to have that moment where its closed to allow the pistons downward movement to push the air and fuel into the transfer ports into the combustion chamber. We wouldnt half to worry about this if we had a reed cage. If there are some people in the forum that can make some reed cages for chainsaws, I would buy one. The reed cage is awesome imo because as soon as that piston starts going down it closes and you get almost the entire downward pressure of the piston to pack all the air and fuel into the combustion area. Meaning you can open your intake as far as you like almost. Anyways, back to the piston ported engine, so when working on the intake side just remember there has to be some time in there to allow the piston to push the fuel and air into the transfers,and into the combustion area so just watch the rhythm of your engine and think of it like a song in your head the best i can decribe it is with a tune.



I tried,alot of capitalization and a whole lot of periods and commas.


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## edisto

You can get an electronic copy of Jenning's book here. The specific numbers might not be right for chainsaws, but it is a great overview of the basic principles of porting, and the important considerations.


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## edisto

freehandslabber said:


> Say what you will about Tomtree's posts ,however undecipherable ,the man does some uber gnarly tree work.....his pictures are much better



You've got me wrong! I love Tom Trees' posts!


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## pepsifreak28

Here is a link to the files I like to use.
http://www.lockpicks.com/browseproducts/12-Piece-Needle-File-Set.HTML

They work great for reaching the hard to get areas.

Thanks for the edit on my run-on post freehand I can't edit the post to replace the text for some reason.


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## J.W Younger

edisto said:


> This is your post:
> 
> 
> 
> This is your post on crystal meth:
> 
> 
> 
> Any questions?


that made me laugh but I like tomtrees and didn't even notice this thread was'nt puntiated


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## Freehand

edisto said:


> You've got me wrong! I love Tom Trees' posts!



LOL


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## TraditionalTool

*Here's a couple more photos*

pepsifreak,

Here's a couple more pics, I'm not sure exactly what angle you need.

Here's one looking into the cylinder, leaning to see the exhaust side.






Here's a couple of the exaust:


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## pepsifreak28

I'm going to post some pics for TraditionalTool
these are not exact porting but rather ideas pointing out where you have metal to work with.

Porting is an art it takes a little practice.

I think the hardest part is getting everything even and not going to far that's why I say use a file to start out it does take longer but a dremel can cut very fast if you do use a dremel a stone is better than a carbide bur for starting out.

Anyways here is some pics the red means where you have some room to work with based on the pictures feel free to toss in some ideas and such but don't be afraid to try it get some files and go for it.

If your afraid of the piston ring popping out most of the time it happens when you go to wide around the bore and exceed the circumference of the piston. 
As far as free porting you can get an idea how far you can go by seeing how far the skirt of the piston travels in the bore. 
File a little and recheck if your worried about things like that and making holes. Just look on the outside of the jug to see about how much metal is on the outside..


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## TraditionalTool

pepsifreak28 said:


> I'm going to post some pics for TraditionalTool
> these are not exact porting but rather ideas pointing out where you have metal to work with.


Ok, would like to understand some guidelines on what you are trying to accomplish.


pepsifreak28 said:


> Porting is an art it takes a little practice.
> 
> I think the hardest part is getting everything even and not going to far that's why I say use a file to start out it does take longer but a dremel can cut very fast if you do use a dremel a stone is better than a carbide bur for starting out.


I think I have some stones, but not sure they will fit my dremel. I can get a bit for the dremel if I need.

I won't have my piston for a couple days, so can play with this cylinder, I need to clean it up also, it is still scorched inside.
Anyways here is some pics the red means where you have some room to work with based on the pictures feel free to toss in some ideas and such but don't be afraid to try it get some files and go for it.

If your afraid of the piston ring popping out most of the time it happens when you go to wide around the bore and exceed the circumference of the piston. 
As far as free porting you can get an idea how far you can go by seeing how far the skirt of the piston travels in the bore. 
File a little and recheck if your worried about things like that and making holes. Just look on the outside of the jug to see about how much metal is on the outside..

On the following pic, are you trying to thin the wall from the inside to narrow the inside, enlarging the chamber effectively?

And what about the mark you have on the left center fin, are you trying to thin that out so it is thinner? How much would you take, as a target?





Then open the exaust to allow more flow out.

However, could you explain the theory behind the intake and exhaust ports inside the cylinder? Seems that the ceiling is being raised on the exhaust substantially, to even that out, at least I think that is towards the top the cylinder. The intake you just take it slightly as it is pretty even already??? The exhaust is raised to even out with the corners pretty much. Is that right? Or is that just coincidental?


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## TraditionalTool

I have a small orange cylinder stone in my dremel box, and I have one of these which is tungsten carbide. Will this work? (it's small tip)

I don't know if I can cut metal with this bit...






EDIT: it says soft metal, that's not a cylinder though, is it?


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## pepsifreak28

Well the exhaust port is pretty wide to begin with the curve part of it meaning the port pretty well wraps around the piston in the jug so if you went wider making the port go further around the piston you might get it too wide and the ring will pop out
you could make the port taller meaning working on the roof of the port (the part close to tdc) and a little on the bottom to widen the "smile" of the port to give more flow.

the first pics i posted of the dirt bike jug you can see how they make knife like edges that's what the little line ment on the jug i forgot to do the other side.
The intake you can widen it a little but the intake should be ok the way it is if your afraid to mess with it worse case is if you go to far on the intake you would just half to make you a reed cage and a reed cage isn't a bad thing
If it was to happen. 
But making the intake open a little more helps.

The transfers on the bottom (the one with the four arrows) you have some room to work on the sides to widen a little just don't forget your gasket has to sit on it.

porting is more or less shapeing the ports and making the flow better granted you can change the timeing and such but the only timeing you really half to worry about is the intake side and if you mess that up you can just make a reed cage and your back in business.

when I say a reed cage a reed is a thin pieace of metal that only flows one way. 
On a piston ported engine the piston acts like a reed valve in a way.
The good thing about a reed is that as soon as the piston goes down in the jug the reed snaps shut and forces the air and fuel into the combustion chamber so in a way you get the full downward pressure to push the fuel into the combustion chamber.

On piston timed engines like chainsaws and weed wackers there is a moment that the intake opening is closed but there is still downward movement of the piston so the rest of that travel is used to push the air and fuel into the combustion chamber.


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## pepsifreak28

That bit would be fine files even drill bits work too anything that will grind the metal. 
The jug isn't that hard of a metal the coating isn't super hard either you would be suprised how fast you can take metal down with just a round chain file.


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## sawinredneck

TT take that boot off the intake and take some pics of the intake side, that is where 90% of the work needs to be done on that cylinder.
On the transfers, just smooth everything around the edges and bring the centers to as much of a point as you can to "encourage" the air to move smoothly.


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## TraditionalTool

pepsifreak28 said:


> Well the exhaust port is pretty wide to begin with the curve part of it meaning the port pretty well wraps around the piston in the jug so if you went wider making the port go further around the piston you might get it too wide and the ring will pop out


Yeah, that makes sense. And in that regard it seems that the center fin of the tranfer ports would need to be flat to provide support for the ring as well.


pepsifreak28 said:


> you could make the port taller meaning working on the roof of the port (the part close to tdc) and a little on the bottom to widen the "smile" of the port to give more flow.


I've read that it's not good to stop modifying the roof and bottom too much. Is that true?


pepsifreak28 said:


> The intake you can widen it a little but the intake should be ok the way it is if your afraid to mess with it worse case is if you go to far on the intake you would just half to make you a reed cage and a reed cage isn't a bad thing
> If it was to happen.
> But making the intake open a little more helps.


I've taken some pics per redneck's comments, but your comments and his seem to conflict. It doesn't seem like that is that much to play with on the intake, where he says that is where most of the work needs to be done. You had very little marked on the pic above for the inside of the intake port. I don't see much on the outside, but some can open up, certainly.

I don't understand the center fin of the transfer ports, so I just want a knife edge along the top, or on the inside edge of the cylinder?

The transfers on the bottom (the one with the four arrows) you have some room to work on the sides to widen a little just don't forget your gasket has to sit on it.

porting is more or less shapeing the ports and making the flow better granted you can change the timeing and such but the only timeing you really half to worry about is the intake side and if you mess that up you can just make a reed cage and your back in business.

when I say a reed cage a reed is a thin pieace of metal that only flows one way. 
On a piston ported engine the piston acts like a reed valve in a way.
The good thing about a reed is that as soon as the piston goes down in the jug the reed snaps shut and forces the air and fuel into the combustion chamber so in a way you get the full downward pressure to push the fuel into the combustion chamber.


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## TraditionalTool

This is the other stone I have for the dremel.

This would work also, it's aluminum oxide.


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## TraditionalTool

pepsifreak28 said:


>


I see what your talking about now, how the edge is knife like along the edge.

In my case I wouldn't want to touch the inside flat area of the cylinder wall, I don't think. Only the top ridge, right?

Sorry for all the Qs, I almost understand what I need to do. Thanks so much for the help.


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## edisto

TraditionalTool said:


> I see what your talking about now, how the edge is knife like along the edge.
> 
> In my case I wouldn't want to touch the inside flat area of the cylinder wall, I don't think. Only the top ridge, right?
> 
> Sorry for all the Qs, I almost understand what I need to do. Thanks so much for the help.



TT hold up!!!

Don't start cutting yet!

From what I can see of Pepsi's red lines, you are going to get yourself in trouble.

When just starting out, you do _not_ want to cut on the top and bottom of the ports, as that will affect timing. Down the road maybe, but your initial work should just be to widen the ports.

For the exhaust, you might want to increase the width (measured across the port, not along the circumference of the cylinder) to 60-65% of the bore diameter. More than that and you have to be careful about short-circuiting (charge going directly from the transfers to the exhaust). 

When widening, you need to be keep 3 things in mind in addition to not getting too close to the transfers: 

1. Leave 2 mm of piston skirt seal on either side of the edges of the port. 

2. Widening the port puts stress on the rings because they have to pop in to the port and be squeezed back into the cylinder. This means that as you widen, you need to maintain or exaggerate the oval shape of the cylinder, and chamfer the edges of the port. It also means the port must be symmetrical on either side of the vertical axis. An uneven window will shift the ring as it moves in and out, and can cause the edge of the ring to push against the pin in the groove, eventually working it out and allowing the ring to spin. if that happens, you'll catch an edge in the port for sure.

3. Don't cut the roof or the floor of the port. At least not yet. There are plenty of gains to be had by widening. Increasing the duration makes the power curve much more peaky than gains gotten from widening.

As for the transfers, you can clean them up and work on the bottom, but other than that, you should leave them alone for the time being. Widening the transfers typically boosts the mid-range, not the peak.


----------



## TraditionalTool

edisto said:


> 1. Leave 2 mm of piston skirt seal on either side of the edges of the port.


I'm not sure I understand this.


edisto said:


> 2. Widening the port puts stress on the rings because they have to pop in to the port and be squeezed back into the cylinder. This means that as you widen, you need to maintain or exaggerate the oval shape of the cylinder, and chamfer the edges of the port. It also means the port must be symmetrical on either side of the vertical axis. An uneven window will shift the ring as it moves in and out, and can cause the edge of the ring to push against the pin in the groove, eventually working it out and allowing the ring to spin. if that happens, you'll catch an edge in the port for sure.


I thought this is what pepsi was trying to explain.


edisto said:


> 3. Don't cut the roof or the floor of the port. At least not yet. There are plenty of gains to be had by widening. Increasing the duration makes the power curve much more peaky than gains gotten from widening.


This is what I was asking about as it is what I had heard.


edisto said:


> As for the transfers, you can clean them up and work on the bottom, but other than that, you should leave them alone for the time being. Widening the transfers typically boosts the mid-range, not the peak.


Ok, I'm still trying to understand what I want to cut/grind out. Now I'm not clear...:monkey:


----------



## scotclayshooter

TraditionalTool said:


> I have a small orange cylinder stone in my dremel box, and I have one of these which is tungsten carbide. Will this work? (it's small tip)
> 
> I don't know if I can cut metal with this bit...
> 
> 
> 
> 
> 
> 
> EDIT: it says soft metal, that's not a cylinder though, is it?



I used one of those to do my 262XP works well but cloggs up so keep spraying it with WD40.

I soaked mine it caustic soda with warm water a few times and it took the aluminium out and didnt damage the bit.


----------



## edisto

TraditionalTool said:


> edisto said:
> 
> 
> 
> 1. Leave 2 mm of piston skirt seal on either side of the edges of the port.
> 
> 
> 
> 
> I'm not sure I understand this.
Click to expand...


If you make the port too wide, you'll be wider than the piston surface if there is a cutaway for the wrist pin or for a window.




TraditionalTool said:


> Ok, I'm still trying to understand what I want to cut/grind out. Now I'm not clear...:monkey:



TT...go back to post #22 and follow the link I have there. There is a pdf of Jenning's book, which explains all of the principles and tradeoffs that you need to understand. The actual time-area numbers might not be applicable, but the approach is.


----------



## TraditionalTool

edisto said:


> go back to post #22 and follow the link I have there. There is a pdf of Jenning's book, which explains all of the principles and tradeoffs that you need to understand. The actual time-area numbers might not be applicable, but the approach is.


Ok, I'm chilling with Jennings...interesting reading...I guess there is no real short cuts...


----------



## sawinredneck

TT IF you want to raise or lower all you are going to take out is .020-.040" THATS IT!!! Very litle changes make big changes in performance!
Concentrate on cleaning things up and making it flow.
What I was reffering to on the intake side is you want to widen it about as much or more than the exhaust side. Compare the two and you will better understand. Also you need to "bellmouth" for lack of a better word the inlet of the intake so you can make as much use of the air coming in, but leave enough srength. Think of it this way, all of the intake gases fill the intake tube, then meet that "wall" on the cylinder so they bunch up and swirl around. Your job is to make a smooth transition from the intake tube to the cylinder to the piston. Same with the exahsut, but there isn't as much to work with there.
Yes a "knife edge" is a good way to describe it, I like to leave them a bit more rounded just for strength myself.
Clean up the flashing and polish things up a bit then you can start to see and understand what more can be done. Don't be afraid of it, those cylinders are cheap experiance!


----------



## MS460WOODCHUCK

sawinredneck said:


> TT IF you want to raise or lower all you are going to take out is .020-.040" THATS IT!!! Very litle changes make big changes in performance!
> Concentrate on cleaning things up and making it flow.
> What I was reffering to on the intake side is you want to widen it about as much or more than the exhaust side. Compare the two and you will better understand. Also you need to "bellmouth" for lack of a better word the inlet of the intake so you can make as much use of the air coming in, but leave enough srength. Think of it this way, all of the intake gases fill the intake tube, then meet that "wall" on the cylinder so they bunch up and swirl around. Your job is to make a smooth transition from the intake tube to the cylinder to the piston. Same with the exahsut, but there isn't as much to work with there.
> Yes a "knife edge" is a good way to describe it, I like to leave them a bit more rounded just for strength myself.
> Clean up the flashing and polish things up a bit then you can start to see and understand what more can be done. Don't be afraid of it, those cylinders are cheap experiance!



Do you have any pictures of these type of cylinders already ported?


----------



## TraditionalTool

sawinredneck said:


> TT IF you want to raise or lower all you are going to take out is .020-.040" THATS IT!!! Very litle changes make big changes in performance!


So, that's less than 1/64th of an inch, right? That doesn't seem like much, and I think there are a lot of calculations at play here, The bellmouth you mention before will take it more than that. Just sayin', that in this case I think your talking about raising the roof of the port.


sawinredneck said:


> Concentrate on cleaning things up and making it flow. What I was reffering to on the intake side is you want to widen it about as much or more than the exhaust side. Compare the two and you will better understand. Also you need to "bellmouth" for lack of a better word the inlet of the intake so you can make as much use of the air coming in, but leave enough srength. Think of it this way, all of the intake gases fill the intake tube, then meet that "wall" on the cylinder so they bunch up and swirl around. Your job is to make a smooth transition from the intake tube to the cylinder to the piston. Same with the exahsut, but there isn't as much to work with there.


Yeah, that makes sense.


sawinredneck said:


> Yes a "knife edge" is a good way to describe it, I like to leave them a bit more rounded just for strength myself.
> Clean up the flashing and polish things up a bit then you can start to see and understand what more can be done. Don't be afraid of it, those cylinders are cheap experiance!


Ok, not too worried about the cylinder at this point, even took a file and needle nose and pulled the ring out of the bad piston. In theory I would reuse it by cleaning the ring slot and putting a new ring on it. Doesn't the ring matter mostly in how tight the compression is?


ms460woodchuck said:


> Do you have any pictures of these type of cylinders already ported?


+1


----------



## sawinredneck

The crappy cell phone pics are in this thread:
http://www.arboristsite.com/showthread.php?t=40236&highlight=bubba

Deeper in the thread I go after it again, heres the post with pics: http://www.arboristsite.com/showpost.php?p=535390&postcount=90

Really a lot of information in that thread if you take the time to read and analyze it!


----------



## pepsifreak28

Sorry I haven't been posting today anyways in porting the main thing is you got to give it a try and just clean up and improve the flow.. like redneck said its a learning process..

Understanding how a 2 stroke truly works is a key part I put the 2 stroke video at the first post so you can watch it until your eyes bleed lol 
just because you know the basic operation of the 2 stroke don't mean anything if you watch the video over and over you start to see.... hey wait a minute.. if i do this or that i will get this result..

such as if you move the exhaust port closer to the spark plug you will get an effect of "spark then exhaust" very quickly giving you higher rpms.. but less torque..
and the further i move the exhaust port away from the spark plug i get a "spark wait wait wait then exhaust"
giving the fuel more time to expand and push down on the piston 

and many other things factor in there as well like angle of the port and the duration of the time that the port is open etc etc but those are small effects that you wont notice as much as the other.

The main thing is at first to clean up the casting flaws and improve flow that will allow the engine to breathe I wish i could find a before and after of a ported jug but i was only able to find the ktm pics if anyone wants to show a before and after that would help a lot..


----------



## pepsifreak28

On a side note where is all the machinist/fabricators on the forum must be some out there that are handy with grinders and such I want a bold on reed for the little walbro carbs lol


----------



## J.W Younger

Who was it said "a little knowlege is a dangerous thing"?


----------



## edisto

J.W Younger said:


> Who was it said "a little knowlege is a dangerous thing"?



You did.


----------



## J.W Younger

edisto said:


> You did.


you're right, I did, but I'm not smart enough to come up with that on my own so I must have heard it before.


----------



## TraditionalTool

sawinredneck said:


> Deeper in the thread I go after it again, heres the post with pics: http://www.arboristsite.com/showpost.php?p=535390&postcount=90
> 
> Really a lot of information in that thread if you take the time to read and analyze it!


redneck,

I've read through it and the associated threads, and will go through it again, probably more than once.

Question on the external openings of the ports, where they are radiused/bellmouthed. That is just opened up and doesn't follow the guidelines of not opening but .020"-.040", right? Seems that as long as the inside of the port stays the same, the radius/bellmouth on the outside of the cylinder (what I'm referring to as the external portion of the port) should be softened to provide for the smooth air flow. At least if I understand correctly.

In regard to the inside of the cylinder though, that is mostly where the concerns are with the rings, raising the roof, lowering the bottom, etc...

I realize that each cylinder is different, but just thinking in general and in getting the external portions of the ports opened/softened so that the air will flow well.

And yes, your pics were lousy but I could tell what you were trying to show. Not to worry.


----------



## buck futter

here are some ideas, 
what do you think pepsifreak and TT, would this run ok?

buck


----------



## TraditionalTool

buck futter said:


> here are some ideas,
> what do you think pepsifreak and TT, would this run ok?
> 
> buck


BF,
That looks great to me. I see you seem to have raised the roof on the intake on the inside, but it looks great.

I was thinking to soften the edges on the intake, where the muffler attaches to the cylinder at the outside, but yours looks very clean and I suspect it should flow nicely. However, since you didn't widen it too much, it seems that the ring should have plenty of support.

Have you put this all together?


----------



## blsnelling

Several things I noticed here.

First you show raising the exhaust port. That is something I rarely do. This will cost you compression and torque. If you're after RPMs, you'll get them anyway with a good port job. I typically see about a 1500 RPM increase at WOT without raising the exhaust.

You show raising the intake as well. I'm not sure why you'd want to do this since the intake opens from the *bottom *up. If you want to increase intake duration, you do it by lowering the port and widening.

Be careful enlarging the transfers. Yes, they may flow more volume, but at the expense of velocity.

I *always *widen the ports; intake, exhaust, and transfers. If not, you're not really doing much of a port job. I shoot for intake and exhaust port widths of 70% of bore diameter. This is not always possible though. Sometimes you are limited by skirt width, ring end locations, etc. The transfers I widen and angle towards the intake. I usually raise them a couple of degrees as well, especially if I lowered the cylinder. If you're not comfortable messing with the transfers, then leave them alone. You'll see significant gains without changing them at all.

Port shape is *extremely *critical. The top and bottom of the exhaust port are most critical. The rings travel completely over it with every stroke. They need to be concave, not even flat. When done with port shape it's *very *important to put a bevel back on the top and bottom as well. This helps significantly in keeping the ring from snagging and destroying your work.



pepsifreak28 said:


>


----------



## TraditionalTool

blsnelling said:


> I *always *widen the ports; intake, exhaust, and transfers. If not, you're not really doing much of a port job. I shoot for intake and exhaust port widths of 70% of bore diameter. This is not always possible though.


Brad,

Would love to see how you would go about porting this cylinder, is it possible for you to markup the images?


----------



## buck futter

TT,
yes it ran very well and has been for 2 years now.

I'm not going to say I know it all, I'll leave that for others to tell you.

You need to sift through the sand to get the nuggets of info.


----------



## blsnelling

TraditionalTool said:


> Brad,
> 
> Would love to see how you would go about porting this cylinder, is it possible for you to markup the images?



Simply widen the intake and exhaust to 70% of bore diameter, or what ever the limitations of piston design will let you. I might also widen the transfer closest to the intake, bringing the back edge closer to the intake. I would only widen it as low as what the crown of the piston travels. Watch out for rings ends when widening transfers as well. 

Don't raise or lower any ports at this point. You'll see huge gains with stock timing. 

Don't make the carb side of the intake spigot any larger than the intake elbow.

Widen the muffler flange about as much as you widen it at the cylinder wall. Port match the muffler and gasket.

Install the cylinder without rings and measure squish. Then decide whether to use a gasket or not.


----------



## TraditionalTool

blsnelling said:


> Simply widen the intake and exhaust to 70% of bore diameter, or what ever the limitations of piston design will let you. I might also widen the transfer closest to the intake, bringing the back edge closer to the intake. I would only widen it as low as what the crown of the piston travels. Watch out for rings ends when widening transfers as well.
> 
> Don't raise or lower any ports at this point. You'll see huge gains with stock timing.
> 
> Don't make the carb side of the intake spigot any larger than the intake elbow.
> 
> Widen the muffler flange about as much as you widen it at the cylinder wall. Port match the muffler and gasket.
> 
> Install the cylinder without rings and measure squish. Then decide whether to use a gasket or not.


Thanks Brad, this seems to be a good rule of thumb to go by.

So, my bore is 44mm, and if I understand you correctly, your saying don't go beyond 30mm wide (30.8 is 70 percent).

Could you explain the skirt so I can determine if there is any conflict with widening it to 30mm? Edisto mentioned that if the piston has inlets for the crankshaft, that could present problems. I have the old piston out of the engine and can take pics or measure if something would help you to determine that.


----------



## edisto

TraditionalTool said:


> So, my bore is 44mm, and if I understand you correctly, your saying don't go beyond 30mm wide (30.8 is 70 percent).



Just remember that that is the length of the chord, not the circumference of the cylinder.



TraditionalTool said:


> Could you explain the skirt so I can determine if there is any conflict with widening it to 30mm? Edisto mentioned that if the piston has inlets for the crankshaft, that could present problems. I have the old piston out of the engine and can take pics or measure if something would help you to determine that.



Hopefully a pic will help. I superimposed a port shape onto a piston. The recommendations I have seen are for 2 mm of skirt past the port (on either side) for a good seal. You can see that widening the port past the edges of the skirt would prevent any seal at all.






So just measure the (skirt width - 4mm), and 70% of the bore diameter, and go with the smallest of the 2.


----------



## blsnelling

70% as measured along the curve of the cylinder wall.


----------



## TraditionalTool

blsnelling said:


> 70% as measured along the curve of the cylinder wall.


Thanks Ed and Brad.

I put the old piston in the cylinder and marked the sides of the current intake and exhaust with a magic marker, then pulled it out and measured with a flexible rule. Currently both are about 25mm (approx.), so I have about 5mm of width I can take it. I won't touch the roof or bottom of the ports, per your recommendation.


----------



## edisto

blsnelling said:


> 70% as measured along the curve of the cylinder wall.



That explains it...I thought 70% was getting a little on the edge.

Just out of curiosity, why do you measure along the curvature instead of measuring actual port width? My trig might be off, but the end result of this is that as bore size increases, you wind up with smaller ports relative to making port width, i.e., chord, a direct function of diameter.


----------



## sawinredneck

TT if you read the threads I widened around .120" on the intake and exhaust. The .020-.040" is STRICTLY up and down! Open the throat from the intake tube as much as you dare, I'm not sure where Brad came up with this information? MAKE IT FLOW!!!
Brad without a base gasket he exaust need raised to keep timing in check. I also like to lower the intake for more airflow. RPM's are not my thing I want tourqe, which may be why I despise the 346xpoe so much, but I want usabel power, which is what the mods to the 350 gave me.


----------



## blsnelling

sawinredneck said:


> Open the throat from the intake tube as much as you dare, I'm not sure where Brad came up with this information? MAKE IT FLOW!!!



I'm talking about the transition point where the intake elbow meets the spigot of the cylinder. You can open it up as big as you want, but it's not going to flow any more than what the size of the elbow can flow. From there I taper it to the port wall, keeping the walls as straight as possible from spigot to wall.


----------



## matt9923

This has some dam good info. 
anyone have a shot cylinder i could practice grinding on?


----------



## sawinredneck

blsnelling said:


> I'm talking about the transition point where the intake elbow meets the spigot of the cylinder. You can open it up as big as you want, but it's not going to flow any more than what the size of the elbow can flow. From there I taper it to the port wall, keeping the walls as straight as possible from spigot to wall.



You and I are in the same book, just on the wrong page Brad. I'm talking about where the intake tube meets the cylinder, there is a huge wall that creates a swirl there, the more you can thin those walls and utilize the gasses coming in, the better ANY saw will run. It's all about transitions, the smoother the transition the happier anything will be, agreed?
That "elbow" is easily flowing 3/4's more air than the cylinder can take on these saws. It's a bottleneck that gains huge amounts if you think about it.


----------



## Tzed250

sawinredneck said:


> You and I are in the same book, just on the wrong page Brad. I'm talking about where the intake tube meets the cylinder, there is a huge wall that creates a swirl there, the more you can thin those walls and utilize the gasses coming in, the better ANY saw will run. It's all about transitions, the smoother the transition the happier anything will be, agreed?
> That "elbow" is easily flowing 3/4's more air than the cylinder can take on these saws. It's a bottleneck that gains huge amounts if you think about it.



You have to be careful porting the intake back near the manifold...real easy to port to daylight in that area...


----------



## TraditionalTool

blsnelling said:


> 70% as measured along the curve of the cylinder wall.


Brad,

For clarification, this means 70 percent of the piston diameter being measured along the circumference of the cylinder wall. Is that right?


----------



## TraditionalTool

Got the cylinder pretty clean, using draino, I still have just a tad left, there's one alu bugger left in there I can feel...you can barely see it about 3/4 of the way to the right of the exhaust port. There is also a bit of smegma in the top of the cylinder above the exhaust port (towards the bottom in this pic).

This is the before pic:






And after cleaning up:






And I did this muffler mod, which I copied some of the ones Brad has done with these deflectors I got from Baileys.






Tomorrow I will finish getting the cylinder prep'd and widen the ports.


----------



## edisto

TraditionalTool said:


> Brad,
> 
> For clarification, this means 70 percent of the piston diameter being measured along the circumference of the cylinder wall. Is that right?



That amounts to a port width of about 50% of the bore diameter, which is relatively mild.

A port width that is 70% of the bore diameter could get you into trouble with short-circuiting from the transfers to the exhaust.

The problem I have with Brad's 70% rule, being measured along the circumference, is that (unless my math is wrong), in a relative sense, porting by that rule will get progressively milder for larger bores, which seems counter-intuitive to me.


----------



## TraditionalTool

edisto said:


> That amounts to a port width of about 50% of the bore diameter, which is relatively mild.
> 
> A port width that is 70% of the bore diameter could get you into trouble with short-circuiting from the transfers to the exhaust.
> 
> The problem I have with Brad's 70% rule, being measured along the circumference, is that (unless my math is wrong), in a relative sense, porting by that rule will get progressively milder for larger bores, which seems counter-intuitive to me.


Ed,

I think it has to be bigger than 50%, it seems to be closer to 70%, because the radius is not very severe. Maybe Brad will comment on this????

I got my piston today. Looks ok, nothing to write home about...


----------



## blsnelling

All I can tell you is what I do. I measure the bore diameter and then multiply that by 70%. I then mark that distance on a piece of tape. Then I lay that tape on the cylinder wall and mark the wall.


----------



## TraditionalTool

*On the bevel...*

Brad,

I can see a slight bevel around the exhaust port, as came from the factory. I need to put a bevel similar, around the edges?

I see mostly bevel on the sides and floor, but just ever so slightly on the roof where it would seem needed the most.

I guess as you widen the port, it exposes the roof more, since the sides of the port wrap around the cylinder more. As one widens them, it seems that the roof may be more concern to keep the ring from snaggin' on it, as the sides will not be supporting it as well, after widening. Is this suspicion correct?


----------



## edisto

TraditionalTool said:


> Ed,
> 
> I think it has to be bigger than 50%, it seems to be closer to 70%, because the radius is not very severe. Maybe Brad will comment on this????
> 
> I got my piston today. Looks ok, nothing to write home about...



Yup...had a parenthesis in the wrong place on the computer. Redid it by hand, and it comes to about 64.42%, which is a healthy number.


----------



## TraditionalTool

edisto said:


> Yup...had a parenthesis in the wrong place on the computer. Redid it by hand, and it comes to about 64.42%, which is a healthy number.


Darn parens (and semi-colons), they will fsck a program up quick...oh gee, am I allowed to type fsck on here? The mods will think I'm trying to beat the word censor by using a common term for file system check on unix/linux...*lol*

Makes me yearn to write code once again...maybe I'll find a job and do that...but in the meantime...might as well play with 2-strokes...


----------



## blsnelling

Yes, the roof of the exhaust is the most critical port edge. You must have a bevel there. The wider you go, the more critical it is.


----------



## super3

matt9923 said:


> This has some dam good info.
> anyone have a shot cylinder i could practice grinding on?




Pm me your address,i'll send you one.


----------



## edisto

TraditionalTool said:


> Darn parens (and semi-colons), they will fsck a program up quick...oh gee, am I allowed to type fsck on here?



I blame Excel...it works in radians, so I had to convert, but misplaced a parenthesis, so I was dividing sine theta by 2 instead of calculating the sine of 1/2 theta.

Once I did it by hand, it became pretty clear...70% is a constant proportion of the circumference of a circle, so the degrees occupied by that arc (theta) is a constant as well (approx 80 degrees). If theta is a constant, then sine of 1/2 theta is a constant, which means chord length varies directly with the hypotenuse (the radius).

So...Brad's method of using 70% along the curvature of the cylinder gives a port width equal to 64.4218% of the bore, _for all bore diameters_.


----------



## TraditionalTool

blsnelling said:


> Yes, the roof of the exhaust is the most critical port edge. You must have a bevel there. The wider you go, the more critical it is.


Yes, as I suspected...when you look at the cylinder it seems pretty obvious that as it looses support along the cylinder wall, that there would be a tendency for the ring to want to push out. I will make sure I have a decent bevel, do you do your bevel as a flat, or as a soft curve around the lip? I'm going to take a stab at this tonight. Still have some cleaning yet...


edisto said:


> So...Brad's method of using 70% along the curvature of the cylinder gives a port width equal to 64.4218% of the bore, _for all bore diameters_.


This is a good number to know, and gives a second point of reference. 

A small pair of outside calipers should confirm that, yes, however, I'm about 27mm on the stock exhaust port, and I can only go to 28.16 with your number, so that doesn't seem like I can go too much wider there. Seems I'll need to take most of the removal on the exhaust on the shoulder without widening the port too much, if I understand the numbers.

On the intake I have just a tad more to work with, it's about 24mm. While that is more, that is not too much...and the skirt is about 35mm (chord) on the piston. Seems like I have plenty of skirt, but the amount of widening may be limited, if I'm measuring correctly...(I'm still doing that, seems like I need to go over these numbers better).


----------



## TraditionalTool

blsnelling said:


> All I can tell you is what I do. I measure the bore diameter and then multiply that by 70%. I then mark that distance on a piece of tape. Then I lay that tape on the cylinder wall and mark the wall.


Yep, this is the way to do it, for certain...I have been trying to measure it, and I can get a reading with some very small calipers, but I like the idea of putting the tape on it.

Oh where or where can that blue tape be, oh where or where can you be...

EDIT: Just finished the muffler:

Side:






Front:


----------



## TraditionalTool

*starting the exhaust*

I started opening up the exhaust.

Comments appreciated. Seems I should even it out just a tad more, and still need to work the inside a bit, I took the sides out just a tad but can widen a tad more. Here's a pic of the outside. The inside came out blurry...







Here's the intake that I started.


----------



## TraditionalTool

*What about the back of the muffler?*

Do you open up the back of the muffler more so that it can get the exhaust out easier?


----------



## TraditionalTool

*Progress pics...*

Comments appreciated.

NOTE: I didn't do a lot of measuring, other than measuring the length of the tape to be 70 percent of the diameter. I didn't do too much marking either, but did some. I tried to err on the safe side.

I have a stone also, maybe I should use it?

intake:






exhaust:






intake:






exhaust:


----------



## AUSSIE1

When you look at your ports at the cyl, try and make them reasonably square at the sides. In the corners you are losing some port area, if you get my drift. You don't need an oval port.

Your port, whether inlet or exhaust, from the cyl to the outside should be straight, no curvature.

Open up the muffler to the outer specs of your port.

I use the base gasket as a template.
Check your cases with the base gasket. If the gasket is a good match against the cases, you use this to match your transfers to the gasket/cases.
If you have to blend the transfers in, you don't have to go deep, just nice flowing lines.

Your doing a good job.
Keep at it.


----------



## edisto

TraditionalTool said:


> This is a good number to know, and gives a second point of reference.



If/when you start doing some serious experimentation with porting, you are going to want to know area and time/area, and for those you need to work with the actual port widths.



AUSSIE1 said:


> When you look at your ports at the cyl, try and make them reasonably square at the sides. In the corners you are losing some port area, if you get my drift. You don't need an oval port.



Losing area, yes, but flow should poor through a square port because of the dead space in the corners where the 2 boundary layers meet.

Also, the wider the port gets, the more of a beating the rings take, because they extend farther into the port, and so the oval shape eases them back in.


----------



## TraditionalTool

AUSSIE1 said:


> When you look at your ports at the cyl, try and make them reasonably square at the sides. In the corners you are losing some port area, if you get my drift. You don't need an oval port.


Yeah, I went back and pulled the corners up some, to try and get that funnel shape, but it's still not ideal.

I used a silicon carbide grinding bit (dremel, small green) and it was working ok for a bit, but then I noticed that there is no more stone left....I have a couple aluminum oxide stones also. I haven't tried those yet.


AUSSIE1 said:


> Your port, whether inlet or exhaust, from the cyl to the outside should be straight, no curvature.


The intake was better than the exhaust in that regard, but I cleaned up the exhaust also, a bit more.


AUSSIE1 said:


> Open up the muffler to the outer specs of your port.


Right now it is pretty close to a match. I traced it out on paper to make sure.


AUSSIE1 said:


> I use the base gasket as a template.
> Check your cases with the base gasket. If the gasket is a good match against the cases, you use this to match your transfers to the gasket/cases.
> If you have to blend the transfers in, you don't have to go deep, just nice flowing lines.


I'm not gonna mess with the transfers at all. I don't think I'm gonna do too much more to it. But I will try to flatten the sides up any more that I can.

I need to bevel the roof of the ports on the cylinder side still.

Thanks for the encouragement!


----------



## TraditionalTool

edisto said:


> Losing area, yes, but flow should poor through a square port because of the dead space in the corners where the 2 boundary layers meet.


I think I know what he meant, about the side being straight, rather than square. I tried to soften those corners so that air would flow.


edisto said:


> Also, the wider the port gets, the more of a beating the rings take, because they extend farther into the port, and so the oval shape eases them back in.


I was thinking that looking at it the first time. While a funnel shape is ideal, it seems that if the roof comes down at the corners, it's safer for the rings.

I think that is what your describing with the oval ends.


----------



## AUSSIE1

Roof and floors catch rings, you only need a slight curvature here.
Your sides can be reasonably square with a radius in the corners.
Bevel roof and floors.
Clean up sides being careful not too take to much off.
If you take your sides out to your measurements, beveling here too much will only add to your dimensions.


----------



## AUSSIE1

Stones clog up too easily.
Tungsten carbides are best.
Someone mentioned a wood rasp, files even.
A chainsaw file to finish off.
If you use a file, fit some hose to the end so there's no possibility to damage the bore.


----------



## sawinredneck

Looking good TT I'd smooth the transition on the exhaust side a little more, leading to the muffler, and smooth it out a bit, looks like there are some humps here and there. When running the Dremel think of it as "petting" rather than grinding and see how that works for you.
Some guys like to polish them to a mirror finish, I don't much see the need myself, expecially on the intake side.
I would encourage you to at least smooth the transfers, knocking off the flashing etc. before you put it together. Then if you want to measure gains you can port them later.


----------



## TraditionalTool

sawinredneck said:


> Looking good TT I'd smooth the transition on the exhaust side a little more, leading to the muffler, and smooth it out a bit, looks like there are some humps here and there. When running the Dremel think of it as "petting" rather than grinding and see how that works for you.


I did clean things up last night and funny you mention "petting", as I think I was doing more of that. At first I used a carbide burr bit, the small cone shaped one up in the thread...switched to a green silicon carbide stone and was smoothing things out, until I noticed the stone was pretty much gone... Then I used an alu oxide similar and it was holding up better and I could smooth things out some.


edisto said:


> Some guys like to polish them to a mirror finish, I don't much see the need myself, expecially on the intake side.
> I would encourage you to at least smooth the transfers, knocking off the flashing etc. before you put it together. Then if you want to measure gains you can port them later.


I don't see any flashing around them. Are you just talking about the corners?

Also, what do you use to put a bevel on the roof/floor of the ports? Hard to get the dremel at that angle, so I was gonna try some small files and/or bend a triangular handsaw file so that I can reach back in and hook over the cylinder wall. I know it only needs to be slightly radius'd over.


----------



## blsnelling

TraditionalTool said:


> Also, what do you use to put a bevel on the roof/floor of the ports? Hard to get the dremel at that angle, so I was gonna try some small files and/or bend a triangular handsaw file so that I can reach back in and hook over the cylinder wall. I know it only needs to be slightly radius'd over.



Don't worry about the transfers for now on your first port job.

I use a round stone to bevel the ports. If you don't have one, you can make one by shaping it with the "stuff" you use to dress your chain grinding wheels. I suppose you could grind on concrete a while if you don't have that, lol.


----------



## TraditionalTool

blsnelling said:


> Don't worry about the transfers for now on your first port job.


I'm not going to.


blsnelling said:


> I use a round stone to bevel the ports. If you don't have one, you can make one by shaping it with the "stuff" you use to dress your chain grinding wheels. I suppose you could grind on concrete a while if you don't have that, lol.


I had some grinding wheels that are too big for the dremel, but you know what they say...if you got big stones, flaunt 'em! 

I just used them and abraded the edge to soften it, by hand. You just put a slight bevel on the edge, right?


----------



## blsnelling

TraditionalTool said:


> I'm not going to.
> 
> I had some grinding wheels that are too big for the dremel, but you know what they say...if you got big stones, flaunt 'em!
> 
> I just used them and abraded the edge to soften it, by hand. You just put a slight bevel on the edge, right?



You don't need to worry much about the sides, just the top and bottom. You should only need to bevel where you widened it since you didn't raise or lower the ports. Just extend the bevels that are already in the center.


----------



## TraditionalTool

blsnelling said:


> You don't need to worry much about the sides, just the top and bottom. You should only need to bevel where you widened it since you didn't raise or lower the ports. Just extend the bevels that are already in the center.


Brad,

Wouldn't the center of the roof be the most likely place that the ring would catch in this situation though? As you widen it, seems that exposing more of the ring would present the most danger at the center of the radius.


----------



## TraditionalTool

Unfortunately I got stuck at the DMV with my son, getting him an ID card. Tomorrow morning I need to drive home to college, so won't get to this and get it together until I get back, Sun./Mon. most likely. Will post progress pics when I do.


----------



## edisto

TraditionalTool said:


> Brad,
> 
> Wouldn't the center of the roof be the most likely place that the ring would catch in this situation though? As you widen it, seems that exposing more of the ring would present the most danger at the center of the radius.



If the roof is curved, then when you hit the "stock" part of the roof, that curve should already have eased the ring back into the cylinder a fair amount.


----------



## blsnelling

TraditionalTool said:


> Brad,
> 
> Wouldn't the center of the roof be the most likely place that the ring would catch in this situation though? As you widen it, seems that exposing more of the ring would present the most danger at the center of the radius.



That is correct. Theoretically, you need the most bevel in the center. The flatter the port is, the more that is true.


----------



## TraditionalTool

edisto said:


> If the roof is curved, then when you hit the "stock" part of the roof, that curve should already have eased the ring back into the cylinder a fair amount.


Ah, this makes sense. As the sides raise, the area of the ring which becomes supported is greater in that sense.


blsnelling said:


> That is correct. Theoretically, you need the most bevel in the center. The flatter the port is, the more that is true.


Yes, this also does make sense.

I just got home, long trip to L.A., but will get to play with my 350 tomorrow.

Thanks for the help, both of you and redneck too (even pepsifreak for starting this thread.


----------



## pepsifreak28

Thanks TT I have been watching the thread, been busy myself this past week end with a helping with a pig roast yummie...

Lots of good expert advice from many I hope it keeps going with more pictures and can make a reference to bl's thread and this one on porting from start to finish keep the pictures coming


----------



## matt9923

I got a cylinder i can practice on thanks to super!!! :yourock::yourock:

I will reread this this week and take pictures and get involved. 
What should i use a carbide burr? or start with a slower stone.


----------



## TraditionalTool

matt9923 said:


> I got a cylinder i can practice on thanks to super!!! :yourock::yourock:


Excellent! Keep us posted on your progress.


matt9923 said:


> I will reread this this week and take pictures and get involved. What should i use a carbide burr? or start with a slower stone.


There is some good info in this thread, at least there was for me.

I have my saw back together with the modified muffler on it, the cylinder ported, and all seems ok. I will fire it up tomorrow.

Modified muffler reinstalled.







Left side of reassembled saw.


----------



## Terry Syd

*Ring edge*

I also think it is prudent to look at the ring/s. If the ring has a sharp edge you may want to take the edge off with a bit of emery cloth or very fine carborundum sandpaper. 

If you do leave a small spot of unbeveled port window, the ring can still get past it without causing an impact between two horizonal surfaces.

I don't bevel my ports. I use a bit of fine sandpaper on the end of my finger and pull/push it across the newly ported area. You can tell with your naked finger if the edge is still sharp.

If I am trying to get the transfers to direct the flow, then I don't want a bevel on the nozzle end of the transfer, I want the flow to be tight so there will be less mixing and shortcircuiting. I just use the sandpaper to take the edge off. On the exhaust a bevel is ok as it can help direct the flow into the port.


----------



## edisto

Terry Syd said:


> I also think it is prudent to look at the ring/s. If the ring has a sharp edge you may want to take the edge off with a bit of emery cloth or very fine carborundum sandpaper.



Best to leave the beveling for the cylinder and let the rings do their job. 



Terry Syd said:


> I don't bevel my ports. I use a bit of fine sandpaper on the end of my finger and pull/push it across the newly ported area. You can tell with your naked finger if the edge is still sharp.



From what I've read, the bevel is as important or more important than the curve of the port in easing the rings back into the cylinder.



Terry Syd said:


> If I am trying to get the transfers to direct the flow, then I don't want a bevel on the nozzle end of the transfer, I want the flow to be tight so there will be less mixing and shortcircuiting. I just use the sandpaper to take the edge off. On the exhaust a bevel is ok as it can help direct the flow into the port.



I fail to see how a bevel on the top or bottom would lead to short-circuiting, or increased mixing. It would tend to slow the flow slightly, but that's not a bad thing, as it has been found that increasing velocity by decreasing crankcase volume can lead to turbulence that will increase mixing. Of course, transfer ports generally are the narrowest of the ports, so the inportance of the bevel is diminished somewhat.


----------



## timberwolf

> Originally Posted by Terry Syd
> I also think it is prudent to look at the ring/s. If the ring has a sharp edge you may want to take the edge off with a bit of emery cloth or very fine carborundum sandpaper.
> 
> Best to leave the beveling for the cylinder and let the rings do their job.



+100% sanding the edge of the rings is a bad idea, to work rings must have pressure on the back side to make a seal, if there is a bevel on the front side it will allow cylinder pressure to move down the front side of the ring and will work against the pressure on the backside to unseat the ring and increase blow-by causing loss of charge purity and power, also at higher RPM unseating rings can cause problems with ring flutter.

Bevel is importaint, esp the wider the ports get. However the plating is only a few thou thick so it is surprising how little bevel is really needed. A shallow angle bevel is a lot beter at coaxing the rings into place than rounding the edge off.

Also Having absolute square edges on the discharge edge of a outlet actually causes more resistance to flow and turbulence than having a slight radius on the edges of the discharge orifice.


----------



## TraditionalTool

timberwolf said:


> +100% sanding the edge of the rings is a bad idea, to work rings must have pressure on the back side to make a seal, if there is a bevel on the front side it will allow cylinder pressure to move down the front side of the ring and will work against the pressure on the backside to unseat the ring and increase blow-by causing loss of charge purity and power, also at higher RPM unseating rings can cause problems with ring flutter.
> 
> Bevel is importaint, esp the wider the ports get. However the plating is only a few thou thick so it is surprising how little bevel is really needed. A shallow angle bevel is a lot beter at coaxing the rings into place than rounding the edge off.
> 
> Also Having absolute square edges on the discharge edge of a outlet actually causes more resistance to flow and turbulence than having a slight radius on the edges of the discharge orifice.


Thanks Ed and Timberwolf, I didn't touch the ring at all, only put a slight bevel on the roof, and just a touch on the floor, but I only used a grinding stone, moving it by hand across the edge. So it is very slight in that regard.

Good news is that it fires up and runs. I still need to tune it, it doesn't stay idling and I suspect just an adjustment on the idle screw will do it. Unfortunately my wife is teaching a cooking class right now and I don't want to bother them, so waiting until she is finished with them.

It sounds healthy, although I know that the cylinder wasn't perfect, it seemed a very slight area could have had the nikisil wore through, it was however smooth to the touch. I'll find out more after I get it running smoothly and let the rings set.


----------



## SWE#Kipp

timberwolf said:


> +100% sanding the edge of the rings is a bad idea, to work rings must have pressure on the back side to make a seal, if there is a bevel on the front side it will allow cylinder pressure to move down the front side of the ring and will work against the pressure on the backside to unseat the ring and increase blow-by causing loss of charge purity and power, also at higher RPM unseating rings can cause problems with ring flutter.
> 
> Bevel is importaint, esp the wider the ports get. However the plating is only a few thou thick so it is surprising how little bevel is really needed. A shallow angle bevel is a lot beter at coaxing the rings into place than rounding the edge off.
> 
> Also Having absolute square edges on the discharge edge of a outlet actually causes more resistance to flow and turbulence than having a slight radius on the edges of the discharge orifice.



What is the best way to bevel ?
i'm thinking of the tools, burr, mandrel or is there something else that does the job better or easier ??


----------



## blsnelling

I use a round stone and then finish off by hand with fine grit paper.


----------



## Terry Syd

*Chamfer*

I should remind myself not to be too concise when discussing technical issues. OK, here is the longer version.

I think we are on the same page when I see TW write:

“Bevel is importaint, esp the wider the ports get. However the plating is only a few thou thick so it is surprising how little bevel is really needed. A shallow angle bevel is a lot beter at coaxing the rings into place than rounding the edge off.”

Also, Brad writes:

“I use a round stone and then finish off by hand with fine grit paper.”

What we are trying to do is to protect the engine from damage. We want to protect the ring from peeling the very thin coating from the cylinder. The problem I see with the discussion is the term ‘bevel’. For a layman that has never done any porting he views the term ‘bevel’ as being a bevel.

I prefer the term chamfer and more precisely the profile on the chamfer. As TW said, we want a shallow angle to coax the rings back into the piston groove.

We are not trying to put a chamfer on the port that we think is best, we are trying to put a chamfer on the port that the RING thinks best.

The best model for this profile is an old worn cylinder. Take a look at how the rings wear the port windows. There is more wear in the center of the port window than at the edges. That is because the ring is extending further into the port at the center. Further, the wear is not a single angle of say 45 degrees, it is curving profile with the wear blending into the surface of the cylinder. 

You cannot get that profile with a porting tool. You can get it, or close to it, by using a bit of fine sandpaper on your finger tip and touching up the edge of the port. The center of the port will have more profile than the area closer to the edges of the port. You can stick you naked finger in there and feel the difference as you smooth it out.

If you are beveling past the coating and into the aluminum, then you are porting. This is especially true for rear boost ports where the profile can make significant changes in the shape of the power curve at and after peak power.

As far as the ring, you are not putting a ‘bevel’ on it. Think of a knife edge and the difference between a sharp knife and a dull knife. You want to just dull the sharp edge (if it has one). If you take off any more than the thickness of the cylinder coating then you have gone too far. I consider it a prudent check to do after porting. If the ring does catch on the cylinder coating when you fire it up, then you are going to have a whole lot more problems on your hands. Whether you want to check it is a matter for you.

Many rings do come with bevels on the rings. This is especially true for chrome plated top rings. The chrome plating is always smaller than the thickness of the ring and there is a bevel to the full thickness of the ring. Also, some rings come with a taper surface to help promote a rapid break-in period. The taper puts a small surface against the cylinder that quickly wears down and allows the ring to seat early.

Ring flutter is only a problem when the inertia of the ring floats the ring off the bottom ring land and the gas seal is broken. When the ring hits the top of the ring land the gas pressure behind the ring collapses and the ring can be slammed back into the groove by the cylinder pressure.

I do not suggest that anyone ever put a grinding tool into the cylinder to put a ‘bevel’ on the ports. I have seen far too many botched up cylinders with jackasses taking a perfecting good port job (that has taken many hours) and stuffing up the final result. The usual screw-up is that they put the bit on the edge of the port and then move it across to the side of the port, they STOP there and then go back to the other side, where they again STOP, then go back again. The may carry this horrendous ritual out several times. The result is a ‘bevel’ where more material is taken away from the side of the ports than in the center. This is exactly the OPPOSITE of what the ring wants.

Whenever I clean up the edges of the ports, I think in terms of the ring’s requirements. I’ve been doing it this way for over 40 years and I have never had any problems.


----------



## timberwolf

Yeh, looks like we are saying much the same thing just different way of saying it.



> You cannot get that profile with a porting tool. You can get it, or close to it, by using a bit of fine sandpaper on your finger tip and touching up the edge of the port. The center of the port will have more profile than the area closer to the edges of the port. You can stick you naked finger in there and feel the difference as you smooth it out.



Of all the tools to put an edge on a port I do find a round stone the best, with care it is possible to control the point of contact on the round stone to grind an angle on the port edge. It is without doubt a less is more thing and the sides get almost zero, that is a beef I have with stihls latest 460/660 cylinders where the chamfer is close to 1/8th of an inch wide all the way around. Cheep machine work is all that is. You bet I finish the edge too with 600 grit.


----------



## timberwolf

Here is the lower side of an exhaust port I was working on. It's not perfect, but I think a decent job with a round stone. The angle of the cut is fairly constant across the port, but tapers to near nothing at the port edges.

Terry, would this be in line with what you shoot for? Could likely use a little more 600 grit.

Application here is a alky racer motor with port width out as wide as possible with meen piston speed up over 4000 ft/min.


----------



## nmurph

so TW, is the the way all ports should be beveled or is this specific to racing saws with a different taper of the radius for work-ported saws? is the intake beveled differently?


----------



## Terry Syd

*Picture*

TW, a picture is worth a thousand words. We could keep waffling on about what it should look like, but the picture says it all.

I saw the pictures of the Stihls - that was ugly. It was like they wanted to use a shotgun approach to getting the mixture into the cylinder rather than a directed rifle shot. Actually, those pictures would make a good 'what not to do' addition to this thread.

Another thing about the beveling on those ports - timing. A large radius bevel on these over-square, short-stroke engines is going to make a lot bigger timing change than a longer stroke motorcycle engine. I wonder how much timing change occurred from the factory designed specifications. 

By the way, I'm a big fan of yours for all the documentation that you do of your emperical testing - good stuff.


----------



## edisto

timberwolf said:


> Here is the lower side of an exhaust port I was working on. It's not perfect, but I think a decent job with a round stone. The angle of the cut is fairly constant across the port, but tapers to near nothing at the port edges.



If that's what Terry was describing, the we are all talking about the same thing (it tells us what the ring wants preciousssssss...).

The old motorcycle books recommend a 10 degree angle, 0.5mm deep and 2 mm in height. Probably a little excessive for chainsaws? The only rounding, however is right where the bevel meets the port. 

There's a reason they use ramps instead of rounded curbs for wheel chairs. Run some wheels over a square curb, and it will eventually wear to be rounded, but that doesn't mean that is the best design for rolling up a curb.


----------



## TraditionalTool

timberwolf said:


> Here is the lower side of an exhaust port I was working on. It's not perfect, but I think a decent job with a round stone.


timberwolf,

Looking at this make me comfortable with what I did to mine. I used a rounded tip grinding stone, it was easier to get in, but these were designed for running in a die grinder and not a dremel so I just rubbed it by hand along the edge. I didn't take any pics of it though...


----------



## TraditionalTool

Terry Syd said:


> Another thing about the beveling on those ports - timing.


This is something I've been wondering about. How does one go about setting the timing on these saws. I have seen reference to marking the flywheel somehow and using a timing light, but not sure what to do...or even if that can be set.

I know that I really need a tach, and been eying the TechTach 20k. Just not flush with cash right now...it might not be avoidable for this type of work.


----------



## edisto

The reference was to port timing...when the ports are open and closed, not ignition timing, which should be fixed unless you take the key out of the flywheel or use an offset key.

Port timing is altered whenever you use a different-sized gasket, or cut a port to change height.


----------



## TraditionalTool

edisto said:


> The reference was to port timing...when the ports are open and closed, not ignition timing, which should be fixed unless you take the key out of the flywheel or use an offset key.
> 
> Port timing is altered whenever you use a different-sized gasket, or cut a port to change height.


So, how does one calculate the port timing, that must be based on the openings and/or angles of the ports, but somehow the transfers seem to have an effect on all of it.

How does one compensate for changes that are made to the height of the port?


----------



## tdi-rick

edisto said:


> [snip]
> 
> The old motorcycle books recommend a 10 degree angle, 0.5mm deep and 2 mm in height. Probably a little excessive for chainsaws? The only rounding, however is right where the bevel meets the port.
> 
> [snip]



Bell does say 1mm/0.3 deep on all the ports other than the exhaust as the ports are smaller.


----------



## timberwolf

> so TW, is the the way all ports should be beveled or is this specific to racing saws with a different taper of the radius for work-ported saws? is the intake beveled differently?



On a work engine with lower piston speeds, and less exposed ring the port edges can use even less softening. 

Here are some of those ugly stihl ports.... Flame me for saying that.

Especially love the intake, they have chamfers cut where the rings never cross. Just production short cutting I think, likely the port edges are done by some robot at 1000 cylinders an hour.


----------



## Tzed250

A chamfer is a flat plane, normally cut at a 45° angle on the corner formed by two perpendicular planes. Chamfers are specified by a distance parallel with one of the original planes. If there is any rounding, then the term radius comes into play. Since the edge finish on a port is not usually made with a straight sided tool, it normaly becomes a chamfer with radiused corners.


----------



## SWE#Kipp

Thanks everybody for the info about beveling ,, got a 346xp cyl 45cc that i'm working on and have been insecure about how much bevel is needed but now i got a good idea how much is needed 
The pictures from TW was well needed !!!


----------



## Terry Syd

*Cute pock*

Tzed250, I suppose we could call it a 'Cute Pock' - which is a bastardised phonetic pronounciation of the acronym CWTPOAUC (chamfer with the profile of a used cylinder)


----------



## edisto

tdi-rick said:


> Bell does say 1mm/0.3 deep on all the ports other than the exhaust as the ports are smaller.



Indeed, and Jennings makes a similar recommendation. My question was about TW's exhaust port, but I should have elaborated.


----------



## edisto

Tzed250 said:


> A chamfer is a flat plane, normally cut at a 45° angle on the corner formed by two perpendicular planes. Chamfers are specified by a distance parallel with one of the original planes. If there is any rounding, then the term radius comes into play. Since the edge finish on a port is not usually made with a straight sided tool, it normaly becomes a chamfer with radiused corners.



But the chamfer is what does the work. Ideally, the radius should only be on the inside edge of the port chamfer to improve flow.


----------



## nmurph

> CWTPOAUC


this is not an acronym.


----------



## timberwolf

From a very little bit of flow bench testing I have done I found it quite surprising just how much improvment to flow can be had by a very slight softening of a square edge. There is much more to be gained in softening an edge where flow enters a duct from free space though than where it leaves a duct into free space.


----------



## BigJ

timberwolf said:


> From a very little bit of flow bench testing I have done I found it quite surprising just how much improvment to flow can be had by a very slight softening of a square edge. There is much more to be gained in softening an edge where flow enters a duct from free space though than where it leaves a duct into free space.



I recall learnin' this back in fluid dynamics as well. So, any reason to not put a small radius on the sides of the exhaust port? Though, I guess that it's already a fairly large angle exiting the side of the port...


----------



## timberwolf

A radius on the sides is just going to extend the length of the unsupported ring. But the main reason is that 90% of the exhaust flows in the first 10% of port opening or something like that. So by the time the sides of the exhaust port are exposed the transfers are open and any significant exhaust flow is essentially over and done with. What limited flow there will be as part of the end of scavenging will be very low velocity not significantly affected by the coefficient of discharge.


----------



## Tzed250

timberwolf said:


> From a very little bit of flow bench testing I have done I found it quite surprising just how much improvment to flow can be had by a very slight softening of a square edge. There is much more to be gained in softening an edge where flow enters a duct from free space though than where it leaves a duct into free space.



This is why many four strokes respond well to a full radius valve job, as done with a Serdi valve seat cutter. I the '60s and '70s it was the 3-angle valve job, with an angle on each side of the seat. The '80s saw the rise of the 5-angle valve job. The full radius valve job became very popular once the technology to cut them became common.


----------



## TraditionalTool

*Don't forget the limiter tabs on the carb screws!*

To add a point to this thread, do not forget that the carb screws often have tabs on them to limit the screws, and they need to be cut off.

I have mine cut off now, but need to run out and attend to some errands, so won't be able to get around to this until later, to see how I can tune it.

timberwolf,

Seems what your saying is that the intake is more important, with the flow going in, or am I misunderstanding you?


----------



## Terry Syd

*Diffusion*

“From a very little bit of flow bench testing I have done I found it quite surprising just how much improvment to flow can be had by a very slight softening of a square edge. There is much more to be gained in softening an edge where flow enters a duct from free space though than where it leaves a duct into free space.”

TW, this goes to my point about the diffusion of the flow caused by excessive chamfer on the transfer ports. As you mentioned, “there is much more to be gained in softening an edge where flow enters a duct from free space”. This rounding helps the flow bend around into the exhaust port. The converse applies for the transfers, that is, the transfer flow is allowed to bend around the transfer port as it exits.

If we concentrate too much on bulk flow, we can loose sight of the direction of the flow.

The Stihl cylinder is a case in point. The generous chamfers around the entire transfer port will tend to diffuse the flow on the edges. Granted, the bulk flow through the port could possibly be increased, but at what cost to mixing and short circuiting of the mixture.

If we milled the head of the jug, put a glass plate over the cylinder, installed a vacuum pump through the plate, we could watch smoke streams as they entered the cylinder. The generous chamfers should show diffusion around the ports. If the chamfers were tightened up to the edges of the ports we would see less diffusion.

However, in this case, we are seeing the cylinder in isolation – without the valve (the piston) in position. If we add the valve to the ports and move it to where the transfers are just cracking we would see even more diffusion. The piston would still be above the level of the actual port, but the chamfers would be exposed. The chamfers would direct the flow up into the departing exhaust gases and back towards the exhaust port itself. This results in mixing and short circuiting of the incoming fuel mixture. 

Thus, on a transfer port we want to port the transfers for the desired direction of flow and to keep the chamfers to a minimum, essentially, just enough chamfer to accommodate the ring/s.


----------



## tdi-rick

Good point Terry.
With gas flow, any transition is vitally important in terms of flow velocity and volume, but that initial change of direction is most important, and following what Terry said it's possibly worth noting that there is NO bevel on Dolmar/Makita PS7900 transfers at all, they are sharp edged as cast and honed and I'm guessing it and the 681 Solo probably have the best BMEP's of stock saws ATM. 

When you look at the transfers in those jugs a lot of time has been spent on maintaining velocity and direction of flow, with a very generous radius in the duct closest to the exhaust to shoot the stream across the top of the piston with a hell of a twist before the horizontal transition so it's angled straight at the back wall of the cylinder. Without a bevel/chamfer, whoever designed it is making sure that the charge goes straight across the piston crown towards that back wall. There won't be any diffusion and short circuiting going on.


----------



## timberwolf

> Seems what your saying is that the intake is more important, with the flow going in, or am I misunderstanding you?



Not exactly, I don't think.

What I am saying is if you take a pipe squared on both ends you will gain much more by bell mouthing the intake than the outlet side of the pipe. 

It's all due to a viena contracta effect. If the end of the pipe is just a square edged stub the air strams come from all angles and the ones in particular that are comming from 90 deg off to the side of the pipe need to make a sharp bend and the higher the velocity the more they are forced wide in making the turn into the pipe. This creates an eddy just inside the pipe at the wall constricting the cross section of flow to less than the diamiter of the pipe. A bell mouth helps steer the air streams on the outside edge of the pipe into the pipe without them pushing into the center constricting flow.


----------



## Jacob J.

tdi-rick said:


> Good point Terry.
> With gas flow, any transition is vitally important in terms of flow velocity and volume, but that initial change of direction is most important, and following what Terry said it's possibly worth noting that there is NO bevel on Dolmar/Makita PS7900 transfers at all, they are sharp edged as cast and honed and I'm guessing it and the 681 Solo probably have the best BMEP's of stock saws ATM.



Same thing if you look at the early Stihl 044, 064, and 084 jugs. Squared off upper transfer ports with no chamfer, and those saws ran really good. Much better than the updated EPA versions.


----------



## edisto

Jacob J. said:


> Same thing if you look at the early Stihl 044, 064, and 084 jugs. Squared off upper transfer ports with no chamfer, and those saws ran really good. Much better than the updated EPA versions.



It just depends on the width...the transfers are narrow relative to the exhaust, so a bevel is less important there because the cylinder wall keeps the rings from protruding. If it's narrow enough, I suppose you can get away without a bevel, but in any event, you should use less bevel than you would for the exhaust.

As TW pointed out, flow is into the exhaust port, so a small radius inside the bevel effectively increases port area, and improves flow into the port.

The chamfering has to balance 2 different phenomena. If easing the rings back into the cylinder was the only concern, a bevel would do the job, but this has to be balanced with flow considerations.

Like anything you do with a 2-stroke, it's a matter of balancing the tradeoffs.


----------



## crmyers

*Porting tools*

What kind of bits do I need to use in my Dremel for this kind of work? Grinding stones seem to load up in the aluminum.


----------



## TraditionalTool

crmyers said:


> What kind of bits do I need to use in my Dremel for this kind of work? Grinding stones seem to load up in the aluminum.


I showed this in post #30, it is what I used.


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## tdi-rick

edisto said:


> [snip]
> Like anything you do with a 2-stroke, it's a matter of balancing the tradeoffs.




That goes for any engine.

I'd written a long waffle on four stroke porting and engine building in an above post but scrapped it as not relevant but it was saying exactly that.

Everythings a compromise, and for best results you have to try and balance each area.


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## blsnelling

Here's what I do most of my porting with. Go HERE and look at item 8175A23.


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## crmyers

blsnelling said:


> Here's what I do most of my porting with. Go HERE and look at item 8175A23.



Thanks, I'll have to make an order.


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## Terry Syd

*Symetry of flow*

I don't recall anyone mentioning it in this thread, but one of the most important aspects of porting a two-stroke is symetry of the flow.

I use tracings of the port windows to keep the ports the same and to align the exhaust port with the centerline of the cylinder. If you place a piece of paper inside the cylinder and use a soft pencil (I use a broad carpenters pencil) you can trace the outline of the ports and their relationship to each other.

From the tracings you can measure from the side of the exhaust port to the side of the nearest transfer port. You want to get that distance the same on both sides of the cylinder. Use a set of calipers to measure the distance as you want it as exact as possible.

Likewise, after you do a bit of work you can trace the exhaust port to see if the window is symetrical. 

After you get the engine back together again and have run it for a while, you can check the symetry of the flow by looking at the carbon deposits on the top of the piston. If you notice some difference between the two sides, you can go back into the jug and take a look to see what may be causing the difference.

If you never get an exactly perfect pattern, you won't be alone, I've never been able to get it perfect either.


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## TraditionalTool

TraditionalTool said:


> To add a point to this thread, do not forget that the carb screws often have tabs on them to limit the screws, and they need to be cut off.
> 
> I have mine cut off now, but need to run out and attend to some errands, so won't be able to get around to this until later, to see how I can tune it.


All I can say is, WOW, cutting off those tab limiters on the carb helped me to get it running pretty well by just ensuring the screws were out 1 1/4 turns.

Idles much better and seems to run pretty good, but still need to get it dialed in.

Wow, what a great little saw for my $55 investment. It has some roar to it, most certainly...


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## SWE#Kipp

Here are two pics of my first attempt of porting, have only played with the intake and exhaust.
No bevel made on those pics ,,,
So does it look ok, it's just going to be a work saw and it's still waiting for a pop up and lowering of the cyl !
help and advise will be taken gladly


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## AUSSIE1

Nice and neat.
I keep the walls straight with no radius (from the inside out).
Sides a bit squarer (without people thinking I mean a square port!).
Are you going by the 65-70% of cyl rule?
I've noticed the base gasket is a good fit on the crankcase so I match to cyl/transfers to the gasket.


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## blsnelling

Looking real good, especially for your first one. +1 on making the walls straight, from flange to cylinder wall.


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## SWE#Kipp

Thank you guys for the kind words 
Can one of you maybe draw on the photos were to do the changes ??


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## matt9923

I finally have some time to start porting the cylinder super sent me. Thanks again and sorry it took so long for me to do anything with it. 

Its a 46mm, and i took some pictures...


















So i do 46 x 60-70% on the exhaust and put tape inside to know where to grind to. 
46x65%=29.9
46x70%=32.2 
is this rite? 
I don't know what saw it was on and don't know how big to make the intake. 
Their is small bevels on it now but after i widen they should be bigger rite? 

I'm in the proses of rereading the thread for the 3rd time so i will probably find my answers.


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## blsnelling

You'll need the piston to know how wide the skirts are and where the ring ends are.


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## matt9923

blsnelling said:


> You'll need the piston to know how wide the skirts are and where the ring ends are.



hmm, i figured but i don't have one....maybe ill just practice grinding on it and port my 028...


----------



## blsnelling

You might be able to see where the skirts are from the wear marks in the cylinder.


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## matt9923

What is the beast stone type for grinding aluminum? I'm getting the carbide burr for the majority of the work.


----------



## matt9923

Got my carbide burr today. Hope to get some practice in this weekend.


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## mwood1986

*Very insightful information!*

pepsifreak28 and blsnelling Brad - Great information! I thought I knew but now I actually do know! :yourock:
I will be receiving a second cylinder for my 029 super by the end of this week and I am going to attempt on these what you consider "smaller things" and are still pretty big for a newbie like myself. 
I will take all the things I have read into consideration and will have to post pics of course, if I hadn't read this I would have probably butchered it haha

Just one question though lets say I polished everything similar to porting and polishing a car or truck heads. Is it actually beneficial to polish these little two strokes or since it's such a small scale polishing doesn't matter? I would thing it would be beneficial but I figured I'd ask anyhow cause smooth surfaces allow more efficient are transfer.
:deadhorse:
-Mike


----------



## blsnelling

Polished on the exhaust side is fine. On the intake, leave it semi rough. I leave the finish my carbide burr makes.


----------



## mwood1986

blsnelling said:


> Polished on the exhaust side is fine. On the intake, leave it semi rough. I leave the finish my carbide burr makes.



Ok just to clarify I shouldn't mess with what I have marked as #1 since I am new because this changing the timing on this particular cylinder right?

On #2 That's what you were talkin about making 70% of the bore width as long as the clip edges aren't there to catch on the edges

On #3 After I make the width change I then bevel the top and bottom lip a little to insure the rings don't catch
and I can do this to both the exhaust and intake ports or only the inside on the intake and the outside on the exhaust and muffler?






If this is incorrect pls correct me XD


----------



## mustard

More real good detailed porting info on this thread. Good job!!

Any advice on porting a strata engine saw, such as the Ryobi??

Thanks


----------



## JeremyFXDWG

First off I stole this picture from Timberwolf's post earlier in the thread. If that is a problem please let me know and I will take it down ASAP.

The question is in reference to the shoddy "bevel" on the newer factory stihl jugs. When we talk about not changing the port timing I am assuming we are talking about the blue line in the photo. When one ports a jug like this can you remove material from the roof / floor of the port to move the red line toward the blue line till a "normal" bevel is archived basically increasing the interior size of the port past that huge bevel?


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## AUSSIE1

Only do the roof of the exhaust and floor of the inlet.
Leave just a very slight bevel. You don't need much.
A large bevel acts a bit like increased timing anyway.


----------



## scotvl

didn't want to start a new thread to ask one question so here goes. When you widen the exhaust you remove the nikasil on the edge, does this expose the aluminum to more wear than an unported jug or risk the chance of the nikasil flaking off the bore?


----------



## blsnelling

NiSi is not prone to chipping or flaking. Chrome is. I've never seen the NiSi chip on the port edge after a port job.


----------



## scotvl

thanks Brad


----------



## blsnelling

That's not to say it can't. Always put a bevel back on the port.


----------



## scotvl

when doing a woods port on the 84cc bb piston should I just clean up the casting marks or go further and enlarge the windows?


----------



## AUSSIE1

scotvl said:


> when doing a woods port on the 84cc bb piston should I just clean up the casting marks or go further and enlarge the windows?



You can enlarge the windows, just don't sacrifice the strength too much.
The window can look like a jellybean tucking under the pin boss a tad if you get my meaning.


----------



## scotvl

thanks for the help


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## Woodman 460

Very helpful infor. Thx for the thread!:greenchainsaw:


----------



## weimedog

Ok..a question for the pro's...based on an observation and a little experience from the Dirt bike years with old Piston ported two strokes of the late 1970's ..

Subject is strictly intake port & air box relative to crank case volume..assuming things like muffler mods and standard flow related mods to the casting with out changing port timing... YET. (Yea yea I know all these things are inter related)

So I think I have encountered a situation where I think the exhaust flow & scavenging is way more efficient than the intake flow as the saw turned into a torque monster but didn't gain on top, feels like it just ran out of air. And it dawned on me there are a few ways to deal with that.. (Any one remember old KTM 420's? WAY way back when..a story 4 another time )

1) Open up the air box...as the opening is roughly 3/4 the cross sectional area of the exhaust. Also the first link in the (performance) chain that extends all the way to the outlet of the exhaust.
2) Widen the intake port..but it already is....so
3) In crease the intake port duration....and here is the observation:

Small crank case volume..lower the intake at your peril! The less volume means that the pressure rises faster and there is a chance you get the charge to spit back out the intake tract with no reed valve on a piston port machine, Larger crank case volume..more latitude as there is less pressure rise and the column of intake air can pack into that "softer" crankcase.

So on my older big bore J-reds (both an 820 and a 2094) lowering the intake made a tangible change. I want to try to lower the intake on a on a Husqvarna 272 a few degrees, but wonder if the crank case volume is too small to gamble that way.

Anyone ever graft a reed cage from a 60cc dirt bike motor onto a chain saw?

What do you think? And set me straight if I'm way off base.


----------



## Mastermind

weimedog said:


> Ok..a question for the pro's...based on an observation and a little experience from the Dirt bike years with old Piston ported two strokes of the late 1970's ..
> 
> Subject is strictly intake port & air box relative to crank case volume..assuming things like muffler mods and standard flow related mods to the casting with out changing port timing... YET. (Yea yea I know all these things are inter related)
> 
> So I think I have encountered a situation where I think the exhaust flow & scavenging is way more efficient than the intake flow as the saw turned into a torque monster but didn't gain on top, feels like it just ran out of air. And it dawned on me there are a few ways to deal with that.. (Any one remember old KTM 420's? WAY way back when..a story 4 another time )
> 
> 1) Open up the air box...as the opening is roughly 3/4 the cross sectional area of the exhaust. Also the first link in the (performance) chain that extends all the way to the outlet of the exhaust.
> 2) Widen the intake port..but it already is....so
> 3) In crease the intake port duration....and here is the observation:
> 
> Small crank case volume..lower the intake at your peril! The less volume means that the pressure rises faster and there is a chance you get the charge to spit back out the intake tract with no reed valve on a piston port machine, Larger crank case volume..more latitude as there is less pressure rise and the column of intake air can pack into that "softer" crankcase.
> 
> So on my older big bore J-reds (both an 820 and a 2094) lowering the intake made a tangible change. I want to try to lower the intake on a on a Husqvarna 272 a few degrees, but wonder if the crank case volume is too small to gamble that way.
> 
> Anyone ever graft a reed cage from a 60cc dirt bike motor onto a chain saw?
> 
> What do you think? And set me straight if I'm way off base.



opcorn:


----------



## Terry Syd

I'll start, these type of discussions can lead to all sorts of observations.

First, I'd like to hear about the mod you made to the exhaust to turn the saw into a 'torque monster'.

As far as exhaust scavenging on a saw (I assume this comment is related to pressure waves in the exhaust system), I don't see this as possible without an expansion chamber. It would be desireable to get a returning negative wave to the cylinder during the blowdown period, unfortunately the escaping exhaust gases are traveling near the speed of sound - that makes it very difficult for a sonic wave to travel back up to the cylinder when the medium it is traveling in is going as fast as the wave is. 

The exhaust could be tuned to return the negative wave after the cylinder pressure had dropped, which is what happens in an expansion chamber, however with the negative wave pulling the contents of the cylinder out the exhaust port you really need that returning positive wave from the reverse cone to pack the charge back in prior to the port closing.

Essentially, the only viable mod I see to the exhaust on a work saw is dropping the BACKPRESSURE as quickly as possible.

As far as the intake timing and spit back issues. The volume of mixture through the transfer ports is determined by time/area of the ports and crankcase pressure.

At peak torque, the flow of the mixture into the cylinder will have just come to a halt as the piston closes off the transfer ports. Above the speed of peak torque the time is too short to allow all the mixture to flow into the cylinder. If the transfer ports are to remain stock, we can move the point of peak torque higher up the powerband by increasing the crankcase pressure. Along with peak torque being moved higher up the powerband, so does the point of peak horsepower, as now there is more pressure trying to push the mixture through the rapidly closing transfer ports.

So what happens when we increase the intake timing to increase peak power? - We are trying to get a better fill of the crankcase at the higher speeds. 

Which means, since the time/area of the transfer ports remains the same and the calculated crankcase compression ratio remains the same - we are raising the crankcase compression pressure by increasing the volume of mixture that entered the crankcase. More pressure in the crankcase, the faster the mixture flows into the cylinder.

IMO, the first way to improve the intake flow is to reduce pressure drops in the intake system - timing changes should be the last resort. You have widened the intake port, which is good to increase the 'gulp' factor (rate of demand) of the intake system, however, that does not address the issue of what causes the greatest pressure drop (constriction) in the intake system. 

It may be that a slight increase in the size of the carburetor venturi and/or a better filtration system would allow the engine to breathe sufficiently at the higher engine speeds - and allow you to retain the stock intake timing.


----------



## edisto

One factor that seems to get little discussion is intake resonance. Symmetrical opening and closing of the intake create a period where crankcase pressure can overcome the inertia of the charge and push part of the charge back into the intake. Reed valves are one way to deal with this, but intake resonance is another.

Fluid moving through a pipe will return a negative pressure wave when it reaches the end of the pipe. This is the first thing that happens in a tuned exhaust pipe, assisting in scavenging (the second cone on the exhaust generates a positive pressure wave to stuff back some of the charge that was drawn into the exhaust by the negative wave).

The intake functions similarly to the first half of the exhaust, but because it runs into the crankcase, it functions as a resonating flask. The research appears to indicate that the volume of the flask (crankcase) has little effect on resonance relative to the neck of the flask.

If you change the shape of the intake, you change the resonance, and alter the timing at which the negative wave occurs. In other words, the "pull" on the charge provided by the wave no longer occurs at the point where crankcase pressure starts to push mix out of the intake.

The only way to get the right timing for the negative pressure wave is to alter the length of the intake. If you try to find this experimentally, you will need to use a stub exhaust to remove the effects of the exhaust system on the dynamics of the system.


----------



## BloodOnTheIce

With porting a lot of times less, is more.


----------



## weimedog

edisto said:


> One factor that seems to get little discussion is intake resonance. Symmetrical opening and closing of the intake create a period where crankcase pressure can overcome the inertia of the charge and push part of the charge back into the intake. Reed valves are one way to deal with this, but intake resonance is another.
> 
> Fluid moving through a pipe will return a negative pressure wave when it reaches the end of the pipe.



To both who responded thank you! I'm pretty familiar with expansion chamber theory and realize that's not happening on a work saw! Also familiar with the analogy in theory applied to intake tracts.To Terry, scavenging was the wrong concept i was trying to express..u r right takes a cone, a chamber or some other active device to do that...reduced restriction to increase flow is the right description for this situation. To an extreme I believe.

Intake dynamics are where I'm interested. In particular case volume and intake tract mods. The space restrictions on most saws pretty much put an end to the games played in the motorcycle world with later designed two strokes..but the older piston port designs seem to have similar characteristics to these saw motors...so that's why I'm asking if some of the things that worked with them are a valid place to explore on these saws. I understand things are not "apples to apple" because of differences in fundamental design... like bore & stroke and application requirements. Motorcycles were "square" typically. So the entire crank volume was effected by that relative the radically over square saw designs. But I do remember "stuffing" cranks and building reed blocks to allow for more radical (4 the time) intake port timing during that era..and also remember the power output was also somewhat limited by available cooling until water cooling came along!




edisto said:


> The intake functions similarly to the first half of the exhaust, but because it runs into the crankcase, it functions as a resonating flask. The research appears to indicate that the volume of the flask (crankcase) has little effect on resonance relative to the neck of the flask.
> 
> If you change the shape of the intake, you change the resonance, and alter the timing at which the negative wave occurs. In other words, the "pull" on the charge provided by the wave no longer occurs at the point where crankcase pressure starts to push mix out of the intake.
> 
> The only way to get the right timing for the negative pressure wave is to alter the length of the intake. If you try to find this experimentally, you will need to use a stub exhaust to remove the effects of the exhaust system on the dynamics of the system.




This makes sense and I guess I wouldn't have expected the crank volume to literally effect intake resonance frequency, maybe the intensity of the pressure waves both positive and negative. Back to the motorcycle world, there are a variety of intake scheme's trying to find the blend between raw horsepower & usable torque.. I know intake geometry & volume has a whole lot to do with power characteristics. Given that intake geometry is tough to change on saw, my bet also is intake port duration is a place power can be found on piston port saws just as those old motorcycles. Again a place of interest as there isn't much you can do to the intake geometry short of designing one from scratch..not practical..but also where too much duration can ruin your porting day.


So back to the question:

Input on intake port timing relative to crank case volume. There has to be a definable inter relationship between the two. I think I have seen this but I'm not certain, has anyone else? More looking for empirical data vs. theory to either support or refute the rationalizations I have conjured up based I am looking at on a few saws crossed with the experiences I had 30 years ago! Things like the intake port timing experiences on those big slower RPM (stock) saws.

As an aside, I'm real interested in experiences on the 200 series Husqvarna's (600 series Jreds) 272.s 670.s etc. They seem to have small transfers & limited space to open up intake & exhaust so looking else where for power.


----------



## PLMCRZY

Mods need to make this a sticky. Best thread on porting IMO explained just about everything *clearly!*


----------



## Terry Syd

I'm sure your aware of the concept of the 'Boost Bottles' where the intake resonance is tuned. There is an easy way to tune the intake using a straight hose.

The formula is different for a hose vs a resonanting flask such as the Boost Bottle, but I gave up trying to work it out via a formula. I simply put a long, reinforced, plastic hose on the intake system and then used a needle nosed vice-grips to clamp it off at various locations.

As you move the vice-grips along the hose, different volumes are created. Those different volumes would in turn create different resonance characteristics in the intake.

On an enduro bike, a long hose could give me two resonant peaks. I could move one peak to just above idle for torquing along in the rocks, the second peak would occur higher in the powerband. I would adjust the two peaks to give the broadest powerband.

It may be possible to use the hose concept on a saw. The hose should be of a fairly large diameter, but small enough that you could slip it inside the handle of the saw.

At the engine speed that saws run, it may not need a very long hose. You probably won't be able to get the primary (and therefore the strongest) wave where you want it, but you may be able to get one of the other waves to a useful position in the powerband.

After you find the length of hose that gives you the powerband you want, you could then cut it, plug it, and position it inside the handle.


----------



## weimedog

Thanks to all for the time and text book. Good info! And terry's "tuning" concept is a clever concept that should make a difference. Lots of design now goes into the size and shape of everything from the reed block back to the air box & filter these days on the dirt bikes..always a space vs, optimum shape compromise. And while "tuning" is a very important component..its actually the next step after the hard mechanical things like port size & timing along with intake tract and carb configurations are done in my mind to try and optimize the final system.

Yea I remember the Boost bottles, along with other aftermarket wiz bang stuff to hang off the intake tracts over the years, and then the power valves in the exhaust ports..pretty much grew up with and racing motorcycles from my first real race bike, a 1970 Bultaco Sherpa S 200 to the suspension revolution mid seventies to water cooling, active exhaust timing (devices (power valves) thru to the four strokes now. As a former Engineer all that theory was real interesting...but.

I was more curious if any one had real vs. theoretical experience in that area. Some thing quantitative because I know from a life time in the technology world, theory usually comes before empirical data and then gets modified to explain the empirical!!...SO I guess what I have learned is no one has a clue if there is a real relationship..so I'll go out on a limb and say there is..both from what I have seen in the distant past and what I saw again with a Jred 2094 and again with an 820. AND I guess no one has tried to lower the intake on a 272 who's willing to discuss so I'll have to be the one who ruins a few barrels to find out...and report! (Something tangible like how many degree's of rotation gains power if at all and at what point is goes the wrong way! (And that's assuming the other stuff I always do now so what may work for me won't for someone else s configuration..and knowing as a saw building novice, I'm just at the very beginning of a very long curve so please NO one assume I know a damn thing! All I can do is report what I see)


----------



## AUSSIE1

Srcarr52 looks to have played with a few 272's extensively and crankcase compression along with some other 1 and 2 series saws. You don't see him on here very often. Maybe a PM.

Timberwolf has played with the resonance and tuning of the inlet to some extent. He is often lurking around in the background.

Having the means to measure and test seams to be out of reach of most of us. 

Increasing the length in increments wouldn't be difficult but shortening would be another matter with some saws.


----------



## Tohya

Since this is porting 101, I think I'll ask a couple of questions.

1) How close can you make the ports to the ring ends?

1a) Is it better to move the rings ends, or take the easy way out and put the piston in backwards? 

2) On cylinders that have a large chamfer around the ports, would you leave the ports alone or enlarge the ports to get a crisper port opening?


----------



## AUSSIE1

Coupla mil roughly for a work saw.

You can run a piston backwards if the ring ends/ports allow. The 064 piston is run backwards in the 371/2 BB kits for example. 

I'd concentrate more on your port timing firstly.


----------



## Tohya

The roof of the exahust port I'm looking at is flat, it lines up perfectly with the ring groves. And the chamfer is largest off to one side of the port and seems to be the smallest near the center. Which is not what you would want the chamfer to look like. The exhaust duration is 170, as measured with a port map which uses the edges of the chamfers. 

Would you fix the chamfer and/or raise the port to give it a slight arch?


----------



## Terry Syd

That is an already high exhaust port duration, I doubt you want to take it any higher unless you know that the engine needs it. As far as the chamfer, yes, the chamfer should be greater in the center. However, on an exhaust port the flow is going out the port so a chamfer can actually assist the flow as it enters the port (unlike a transfer port where the excessive chamfer diffuses the flow). 

Since the engine is already running with the existing chamfer, I'd leave it alone at the edge of the cylinder lining and trim a bit off the inside of the port where the chamfer is excessive. That should give you a 'flatter' opening of the exhaust port.


----------



## Tohya

I still don't like the looks of the factory chamfers on the jug, but maybe that's just me.  

I remeasured the ports on the 066 BB I have using a depth gauge and a small inspection mirror. I made two measurements, one at the cast port height, and one from the edge of the chamfer.

The roof of the exhaust is 25.96mm from the top of the cylinder and the chamfer is 1mm wide. The top of the transfers are 35.3mm from the top with 1.3mm wide chamfer. The bottom of intake is 63.5mm from the top and had a 1.1mm chamfer.

I used http://www.modelenginenews.org/design/tcalc/TCalcForm.php to calculate the port times, using 111.5mm as the distance from the crank to top of cylinder, and 68mm for rod length, 41mm piston height, 23mm piston Pin offset.

As cast, without the chamfers:
Exhaust: 165
Transfer: 98
Inlet: 174
Blowdown: 33.5

Durations with chamfers
Exhaust: 171
Transfers: 110
Inlet: 181
Blowdown: 30.5


Would fixing the shape of the chamfers and raising the roof of the transfers and exhaust to narrow the size of the chamfers hurt anything? The way I see things, fixing the transfers should reduce the diffusion of the incoming charge. And fixing the exhaust would give a stronger pulse, but that may not make any difference on a saw with a factory muffler.


----------



## Terry Syd

Crikey, who ever put those chamfers on the transfers should be shot. Heck, they are even bigger than the ones on the exhaust port.

The blowdown period on the exhaust is not only related to time, but also to area. Since the pressure differential between the exhaust gases and the ambient air pressure is greatest when the exhaust port first cracks open, it helps to have a large area for flow to quickly vent down the cylinder pressure. You mentioned a 'stronger pulse' - yep, that's what a larger area will give you, that's good, go for it.

You may want to try the jug with the existing transfer ports. Yeah, there will be some diffusion, but the timing change to clean it up would probably make more difference (could be a good or bad move). Try the jug the way it is and see if you like the power. If you think it could use some more transfer area, then you can go back in and clean everything up.

One problem I've noticed with overbored two-strokes over the years is that many times the mod results in insufficient transfer tunnel area to feed the transfer ports. You could have that problem in the existing BB kit. If you raise the transfer ports to clean up that chamfer you could be compounding the problem with the too small transfer tunnels.

It would be a good idea to compute the area at the outlet to the transfer port and see if the existing transfer tunnels can feed that area at BDC. You may find that you need to open up the existing tunnels to feed the transfer ports that you already have. Note that the cross-sectional area of the tunnel should increase as it moves towards the crankcase. 

If the stock tunnels are presently proportioned to the ports and then you open up the port window to get rid of the excessive chamfer, you will likely have to open up the tunnels an equivalent amount to take advantage of the increased port area.


----------



## bowtechmadman

Thanks guys...good read.


----------



## Tohya

Wouldn't the area of the transfer tunnel have more to do with the velocity of the charge? Well, the crankcase volume would affect that as well.

High velocity in the transfers being good for high rpms, but bad for low rmps as it would blow the charge out the exhaust. Since I'm not looking for really high rpms, opening the transfers within the limits of the chamfers and enlarging the tunnels some to keep the velocity down might work out for me. Or maybe just enlarging the tunnels some and leaving the transfers where they are.


----------



## Terry Syd

Note in my previous post that I said that 'the cross-sectional area of the tunnel should increase as it moves toward the crankcase'.

In other words, the 'pinch point' of the least cross-sectional area is the port opening. That will be where the velocity is the highest, at the port window. All you are doing in the tunnel work is to make sure that the ports are adequately fed so that the port windows can do their work.

Think of the transfer port window as the nozzle on a garden hose. The nozzle will direct and control the shape of the water spray - that's what a transfer port window does, it directs and shapes the flow into the cylinder. 

If you put too small of a garden hose on the nozzle, you won't get the pressure or/flow of water at the nozzle. The same thing with the transfer tunnel, you will decrease the delivery of fuel/air mixture AT THE PORT OPENING.

There may be an advantage to moving the pinch point to just before the port opening, but that is a different concept to having too small of transfer tunnels to feed the transfer ports. All I'm suggesting is that you check the cross-sectional area of the transfer tunnels on your BB.


----------



## Tohya

Oh, I see what you are saying.

The tunnel is rather short and the transfers operate under pressure rather than vacuum. So I wouldn't of expected that the area would make much of a difference. It'll be hard to measure, maybe I'll just stuff some silly putty in there and measure that.


----------



## edisto

Pressure or vacuum doesn't make a distance. Sounds to me like you guys are talking about 2 different aspects of the same thing.

All fluids, including air, 'wet' the surface over which they flow. Velocity of flow decreases as you approach the wettable surface, and reaches zero at some point adjacent to the surface. This creates a boundary layer of zero flow (that's why moving fan blades accumulate dust).

If the diameter of a pipe increases, the boundary layer increases in depth and flow slows. What Terry is saying is that for optimal flow, you want the diameter of the transfer (cross-sectional area) to gradually decrease (too rapid of a decrease reduces flow as well) as it approaches the transfer port.

As far as velocity goes, an overall increase in cross-sectional area (maintaining the same tapered profile) will reduce the velocity of the charge. This tends to help mid-range power, not top-end power, but might be a necessary evil if you need more area from the transfers to keep up with changes in the exhaust and intake.

The pattern of flow from the transfers is much more important than time-area for proper scavenging. If the flow is not balanced, scavenging (and therefore performance) will suffer (although this seems to be less noticable at high rpms, so it is possible to see no real ill effects of playing with the transfers, and just not realize the potential optimum).


----------



## Tohya

New question, after doing all that work on the ports in the jug does anyone try to do anything with the rubber intake boot?

The opening in the jug is where the boot connects is ~24mm in diameter. But the inside of the rubber intake boot is about 20.5mm, with a bumpin that narrows it to 17mm for the carb studs.

The two carbs I have have to following specs.

WJ34 Choke: 22.19mm, Venturi: 18.25, Throttle: 21.43

WJ35A Choke: 22.19mm, Venturi: 19.05, Throttle: 21.43

So the area inside the intake is somewhere between the size of the venturi and throttle.

The inside of a 084 intake boot is 26.6mm and it will connect to the jug, seems the intake ports on 084 and 066 jugs are the same size. 

So my current thoughts are, I could either try find a broken 084 tank and try graft the larger 084 carb on to the 066 tank. Or try to bend up a short piece of pipe to fit inside a trimmed 084 boot with tabs under the carb studs to hold it in place and use a little RTV to seal things up.


----------



## Outlaw5.0

I tried to put the 066/660 intake boot onto the 046/460, but the angle and length is wrong and kinks the boot.


----------



## Tohya

Length is the same, the angle is off by about 2 degrees between the 084 and 066. 

The problem is that the 066 boot is for a carb with 31mm bolt centers and the 084 uses 46mm bolt centers.


----------



## Terry Syd

As long as the inside area of the boot is more than the area of the venturi you should be fine. Going to a larger boot without increasing the carb size probably won't get you anything, in fact, you will loose some velocity in the intake.

The reduction in velocity could make the engine more peaky, especially if you have increased the intake duration.


----------



## parrisw

Finally made up a nice degree wheel holder today. Was getting real tired of the crappy mount I half arsed together, and it never ran true which will throw off your measurement. Here are a few pics I think its pretty self explanatory.


----------



## blsnelling

Now *that *is ingenious! I love it!


----------



## parrisw

blsnelling said:


> Now *that *is ingenious! I love it!



Ya, its great. Easy and fast to use, fits any saw, and very accurate!! 
0 runout.


----------



## edisto

parrisw said:


> Ya, its great. Easy and fast to use, fits any saw, and very accurate!!
> 0 runout.



Even lets you measure timing with the cylinder off!

Seriously though...that's bloody clever. If my Riders had won, this would be a landmark day for Canada.


----------



## parrisw

edisto said:


> Even lets you measure timing with the cylinder off!
> 
> Seriously though...that's bloody clever. If my Riders had one, this would be a landmark day for Canada.



Ya its that good EH!! 

Thanks


----------



## edisto

parrisw said:


> Ya its that good EH!!
> 
> Thanks



Just saw my typo...maybe if the Riders had had ONE they would have WON.


----------



## parrisw

edisto said:


> Just saw my typo...maybe if the Riders had had ONE they would have WON.



ahh, ok, gotcha now.


----------



## Tzed250

Nice work Will....!!!

P.S.

Here is a link to my degree wheel setup thread:

*LINK*


.


----------



## parrisw

Tzed250 said:


> Nice work Will....!!!
> 
> P.S.
> 
> Here is a link to my degree wheel setup thread:
> 
> *LINK*
> 
> 
> .



Thanks John. I've read through your thread there many times. That's some nice work too. I like this since it works on anything.


----------



## Andyshine77

blsnelling said:


> Now *that *is ingenious! I love it!



Exactly what I was thinking.


----------



## Tzed250

parrisw said:


> Thanks John. I've read through your thread there many times. That's some nice work too. I like this since it works on *anything*.



That is the cool thing about yours! I tried to do mine with stuff I thought folks might have lying around.


.


----------



## parrisw

Tzed250 said:


> That is the cool thing about yours! I tried to do mine with stuff I thought folks might have lying around.
> 
> 
> .



Ya exactly. Not everybody has a lathe to make this. Though some degree wheels come with spacer adapters, so you may be able to just bolt the degree wheel to the chuck without having to machine a shoulder to make it work. 

Also, your way won't work on a Husky, and that's mainly what I work on.


----------



## Tzed250

parrisw said:


> Ya exactly. Not everybody has a lathe to make this. Though some degree wheels come with spacer adapters, so you may be able to just bolt the degree wheel to the chuck without having to machine a shoulder to make it work.
> 
> Also, your way won't work on a Husky, and that's mainly what I work on.



True!! Yours is "yoo knee vur sul" !!!


.


----------



## parrisw

Tzed250 said:


> True!! Yours is "yoo knee vur sul" !!!
> 
> 
> .



Ya. Thanks!


----------



## tdi-rick

very clever Will, I like it.


----------



## parrisw

tdi-rick said:


> very clever Will, I like it.



Thanks! Now just have to put it to use!


----------



## AUSSIE1

Top idea Will...


----------



## parrisw

AUSSIE1 said:


> Top idea Will...



Thanks Mate! Can't wait to try it out.


----------



## gink595

parrisw said:


> Finally made up a nice degree wheel holder today. Was getting real tired of the crappy mount I half arsed together, and it never ran true which will throw off your measurement. Here are a few pics I think its pretty self explanatory.




You didn't get that idea from Race Saws did ya! LOL... I know I just posted some pics of the same thing a few days back and so did Chevytown, we got the idea from Copsey:hmm3grin2orange:

Thats okay though, you can take credit it for it!


----------



## timberwolf

LOL.

"The secret to creativity is knowing how to hide your sources" _Albert Einstein_


----------



## Tzed250

There is nothing new under the sun....


----------



## CHEVYTOWN13

Remember, he's the *PUTO* that posted Tom's finger ports over here. That PUTO is a ship ready to sink, cuz loose lips sink ships and that PUTO was trying to get credit for Copsey's Trick of the week™????:hmm3grin2orange: Don't even try that #### over there.

Yes, dwell included and an easy set up compared to those CD's he was using:hmm3grin2orange:











BTW, the last poster jumps ships quick depending on the situation...

And oh yeah there is something new about but only those on the inside know the know you know:yoyo:

<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/5gDlHmQkcSk?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/5gDlHmQkcSk?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

Ooops, how did this one get in here...


----------



## TraditionalTool

CHEVYCLOWN,

Are you talking your garbage again, do you ever have anything good to say about anyone?

Using profanity that you learned from your vatos...very classy.

You are real piece of $#!T.


----------



## CHEVYTOWN13

Ah, how cute, traditional fool showed up:hmm3grin2orange:

Oh yeah, I'm a clown for the Evil Empire on a heist for some jugs



TraditionalTool said:


> CHEVYCLOWN,
> 
> Are you talking your garbage again, do you ever have anything good to say about anyone?
> 
> Using profanity that you learned from your vatos...very classy.
> 
> You are real piece of $#!T.


----------



## TRI955

CHEVYTOWN13 said:


> Remember, he's the *PUTO* that posted Tom's finger ports over here. That PUTO is a ship ready to sink, cuz loose lips sink ships and that PUTO was trying to get credit for Copsey's Trick of the week™????:hmm3grin2orange: Don't even try that #### over there.
> 
> Yes, dwell included and an easy set up compared to those CD's he was using:hmm3grin2orange:
> 
> 
> BTW, the last poster jumps ships quick depending on the situation...
> 
> And oh yeah there is something new about but only those on the inside know the know you know:yoyo:



There always has to be one turd in the punch bowl...thanks CT for your thoughts.


----------



## blsnelling

CHEVYTOWN13 said:


> Don't even try that #### over there.



Seems to me you got yourself run off over there too. Drop the gansta rap and you might find yourself accepted with regular Joes.


----------



## CHEVYTOWN13

*Bump for the Puto!*

:spam:


----------



## parrisw

gink595 said:


> You didn't get that idea from Race Saws did ya! LOL... I know I just posted some pics of the same thing a few days back and so did Chevytown, we got the idea from Copsey:hmm3grin2orange:
> 
> Thats okay though, you can take credit it for it!



ha ha. No I didn't actually, I don't visit RSAWS too much. The idea came to me from Dozerdan, he posted a pic for me of the one he made, and the drill chuck came to mind. Like others said, if someone thought of it, someone else is likely too. There are not many new ideas floating around, that's for sure.


----------



## blsnelling

CHEVYTOWN13 said:


> Bump for the Puto!



Is this a confession? Seems you're kind of obsessed with it. Not able to make your points without profanities and vulgarities?


----------



## parrisw

CHEVYTOWN13 said:


> Remember, he's the *PUTO* that posted Tom's finger ports over here. That PUTO is a ship ready to sink, cuz loose lips sink ships and that PUTO was trying to get credit for Copsey's Trick of the week™????:hmm3grin2orange: Don't even try that #### over there.
> 
> Yes, dwell included and an easy set up compared to those CD's he was using:hmm3grin2orange:
> 
> BTW, the last poster jumps ships quick depending on the situation...
> 
> And oh yeah there is something new about but only those on the inside know the know you know:yoyo:




Man you don't know chit. The CD's I was using? How the fuk do you know what I was using. Look back through some of my builds, I've had the same degree wheel you freaking TARD, I've never used a CD. Just goes to show your always talking out of your big FAT ASS. S T F U and go make some dust with your race saws.


----------



## parrisw

CHEVYTOWN13 said:


>



Here's a little tip. Don't make that thing so long, the longer it is the more room for error. Where did ya come up with the axle bolt and nut? Looks pretty sweet.


----------



## edisto

parrisw said:


> Here's a little tip. Don't make that thing so long, the longer it is the more room for error. Where did ya come up with the axle bolt and nut? Looks pretty sweet.



I don't think he actually has it sorted out yet. Look at the first pic...you can't see the shaft.

Now take a close look at the second pic...look towards the top of the degree wheel. See how the pipes in the background don't line up? Notice how the degree wheel is completely perpendicular to the view, but the front face is visible on everything else?

Looks to me like he used Photoshop to put a degree wheel onto the shaft. How sad is that? Novel idea though...

Maybe I should go back and take a closer look at some of his "porting" pics...


----------



## parrisw

edisto said:


> I don't think he actually has it sorted out yet. Look at the first pic...you can't see the shaft.
> 
> Now take a close look at the second pic...look towards the top of the degree wheel. See how the pipes in the background don't line up? Notice how the degree wheel is completely perpendicular to the view, but the front face is visible on everything else?
> 
> Looks to me like he used Photoshop to put a degree wheel onto the shaft. How sad is that? Novel idea though...
> 
> Maybe I should go back and take a closer look at some of his "porting" pics...



I duno, but whatever the fact. It looks like chit. And somewhere some dudes wheel fell off his truck from where Cclown stole that axle nut and stud.


----------



## parrisw

Well lookie here, someone else has done this too. Did a little searching, and look what you find. Man were were you guys when he posted this, so you could run your mouth that he stole the idea from ECopesy.

http://www.arboristsite.com/showpost.php?p=2529143&postcount=7


----------



## funky sawman

:agree2:


parrisw said:


> I duno, but whatever the fact. It looks like chit. And somewhere some dudes wheel fell off his truck from where Cclown stole that axle nut and stud.


----------



## gink595

parrisw said:


> Well lookie here, someone else has done this too. Did a little searching, and look what you find. Man were were you guys when he posted this, so you could run your mouth that he stole the idea from ECopesy.
> 
> http://www.arboristsite.com/showpost.php?p=2529143&postcount=7



Sorry Parris, I just seen you on at RS this past weekend and then all the sudden it seems you had this awesome idea to use a drill chuck, IDK maybe it's silly thinking but I just assumed your awesome idea came from there. I don't know if Eric invented it, I just said that is where I seen it at his shop. As for Super3's picture I think we might have had a converstaion about that at a GTG, so IDK can't say for sure but it might have stemmed from there too. I'm sure Mike will chime in and set it straight.


----------



## CHEVYTOWN13

*What happened to the D Bag?*

I'm not! :hmm3grin2orange:


----------



## parrisw

gink595 said:


> Sorry Parris, I just seen you on at RS this past weekend and then all the sudden it seems you had this awesome idea to use a drill chuck, IDK maybe it's silly thinking but I just assumed your awesome idea came from there. I don't know if Eric invented it, I just said that is where I seen it at his shop. As for Super3's picture I think we might have had a converstaion about that at a GTG, so IDK can't say for sure but it might have stemmed from there too. I'm sure Mike will chime in and set it straight.



Hey, I'd tell ya if I got the idea from there, you know I'm really not that stupid, I know allot of you guys are on here go there as well, and I wouldn't think I could get away with it, seeing how there are way too many people around just looking to discredit someone, and make them look stupid. I was on RS on Sunday or monday, can't remember because Gypo sent me a PM asking why AS was down. Honestly I never saw those pics. I just went and searched around for them last night and found them in the RSbuild section which I never read in. Anyway, I'm not worried about it, just got a little pissed off last night when people start running their mouth about me.


----------



## blsnelling

parrisw said:


> ...seeing how there are way too many people around just looking to discredit someone...just got a little pissed off last night when people start running their mouth about me.



Might as well get used to it. It goes with the territory There are only a handful of haters though. Most everyone else sees it for what it is.


----------



## Mastermind

gink595 said:


> Sorry Parris, I just seen you on at RS this past weekend and then all the sudden it seems you had this awesome idea to use a drill chuck, IDK maybe it's silly thinking but I just assumed your awesome idea came from there. I don't know if Eric invented it, I just said that is where I seen it at his shop. As for Super3's picture I think we might have had a converstaion about that at a GTG, so IDK can't say for sure but it might have stemmed from there too. I'm sure Mike will chime in and set it straight.




Good post Frank. I don't really get all the fussing and back biting BS that goes on. I've given up trying to learn anything from some of the #######s that just show up to kick a fellers nuts. Like the ####### below.





CHEVYTOWN13 said:


> I'm not! :hmm3grin2orange:


----------



## parrisw

blsnelling said:


> Might as well get used to it. It goes with the territory There are only a handful of haters though. Most everyone else sees it for what it is.



Ya, I know. I've just tried to stay away that's all. This is why I have always tried to turn down work.


----------



## blsnelling

parrisw said:


> Ya, I know. I've just tried to stay away that's all. This is why I have always tried to turn down work.



It's unfortunate that it does tend to hinder the hobby side of this for myself. A lot of people assume I show everything I do as a sales pitch. That's simply not the case at all. Sure, it generates work, but that's not why I post what I do. How many saw nuts like yourself do you know locally to share what you do? Probably none. AS is where I go to "show off" and share what I've done. I'm an extravert, and I love sharing my hobby. I love making vids.


----------



## Mastermind

blsnelling said:


> It's unfortunate that it does tend to hinder the hobby side of this for myself. A lot of people assume I show everything I do as a sales pitch. That's simply not the case at all. Sure, it generates work, but that's not why I post what I do. How many saw nuts like yourself do you know locally to share what you do? Probably none. AS is where I go to "show off" and share what I've done. I'm an extravert, and I love sharing my hobby. I love making vids.



An extravert??? No Brad, you have OCD, just like me. 

Some guys have such low self-esteem that attempting to make others look bad is the only thing that makes them feel better about themselves.

I came to AS to learn, and I have learned a lot, from you and many other members. I've seen members with huge amounts of experience leave and never return. Andy comes to mind as I type this, he is sorely missed. At one time, I thought Brad would leave as well. You would be missed too, my friend.

Here's the thing, we are all human, and not one of us is perfect. We would do well do remember that as we travel through life.

Group Hug!?!?!?! :hmm3grin2orange:


----------



## blsnelling

We all know I'm not perfect, lol. The haters have made sure of that. Yes, I'm definately obsessive. That's why stock is never good enough. It doesn't matter what it is.


----------



## TRI955

blsnelling said:


> It's unfortunate that it does tend to hinder the hobby side of this for myself. A lot of people assume I show everything I do as a sales pitch. That's simply not the case at all. Sure, it generates work, but that's not why I post what I do. How many saw nuts like yourself do you know locally to share what you do? Probably none. AS is where I go to "show off" and share what I've done. I'm an extravert, and I love sharing my hobby. I love making vids.



There is nothing wrong with that, keep on keepin on!!

Lets get this back on track...

What is the best tool for doing the upper transfer ports, not much room up there to work with my 4" angle grinder!!!!:biggrinbounce2:


----------



## Mastermind

TRI955 said:


> There is nothing wrong with that, keep on keepin on!!
> 
> Lets get this back on track...
> 
> What is the best tool for doing the upper transfer ports, not much room up there to work with my 4" angle grinder!!!!:biggrinbounce2:



I just cut the jug in half with a chop saw then go at it with my plasma cutter.


----------



## blsnelling

TRI955 said:


> What is the best tool for doing the upper transfer ports, not much room up there to work with my 4" angle grinder!!!!:biggrinbounce2:



I still use a small cutoff wheel exclusively. Rarely do I wish for a right angle tool. Of course if I had one, I might not understand how I ever got by without it.


----------



## Burvol

parrisw said:


> Ya, I know. I've just tried to stay away that's all. This is why I have always tried to turn down work.



Will I believe your a pretty good dude. I always have enjoyed my BC bros, use to live up by your neck of the woods, and I had fun in that province. Good people there. That's a fact.


----------



## sunfish

parrisw said:


> Ya, I know. I've just tried to stay away that's all. This is why I have always tried to turn down work.



I always enjoy the info you post here. Keep it up, man!


----------



## parrisw

blsnelling said:


> It's unfortunate that it does tend to hinder the hobby side of this for myself. A lot of people assume I show everything I do as a sales pitch. That's simply not the case at all. Sure, it generates work, but that's not why I post what I do. How many saw nuts like yourself do you know locally to share what you do? Probably none. AS is where I go to "show off" and share what I've done. I'm an extravert, and I love sharing my hobby. I love making vids.



Your 100% right Brad, I only come here to share and enjoy this hobby, I never do it for any money, any time I've ever helped people out its either for free or very little money just to cover my cost's. And ya I have nobody around here to share with what I do. People just think I'm nuts! Thanks for standing up!



mastermind7864 said:


> An extravert??? No Brad, you have OCD, just like me.
> 
> Some guys have such low self-esteem that attempting to make others look bad is the only thing that makes them feel better about themselves.
> 
> I came to AS to learn, and I have learned a lot, from you and many other members. I've seen members with huge amounts of experience leave and never return. Andy comes to mind as I type this, he is sorely missed. At one time, I thought Brad would leave as well. You would be missed too, my friend.
> 
> Here's the thing, we are all human, and not one of us is perfect. We would do well do remember that as we travel through life.
> 
> Group Hug!?!?!?! :hmm3grin2orange:



Well said!! Agreed



Burvol said:


> Will I believe your a pretty good dude. I always have enjoyed my BC bros, use to live up by your neck of the woods, and I had fun in that province. Good people there. That's a fact.



Thanks man, I appreciate that!



sunfish said:


> I always enjoy the info you post here. Keep it up, man!



Thanks too!


----------



## parrisw

TRI955 said:


> There is nothing wrong with that, keep on keepin on!!
> 
> Lets get this back on track...
> 
> What is the best tool for doing the upper transfer ports, not much room up there to work with my 4" angle grinder!!!!:biggrinbounce2:



I use a dental grinder, contra angle.


----------



## AUSSIE1

For crying out loud, stop the grizzling and get over it.
Remember, two wrongs don't make a right!
This is "porting 101"


I use a right angle as I feel it does a neater and more complete job.

If you want to raise the roof of the transfers and keep them at the same angle, this is the only way.


----------



## whitebutler

*hopeless search*

So I all new on the board so i'm looking for a good hop up for my 390's i bought two last season and want to get more ZING out of them I hope to find some pointers I'm in northern California if i can get a drop on a shop here that would be great :newbie:


----------



## blsnelling

390XP or MS390?


----------



## PLMCRZY

Who cares whos idea it was it looks like it works good. Tell them both Thanks and stop B****IN' 

Some of the stuff that people argue on here is rediculous, its all one big pissing contest. Ill be straight with all of you none of you are gonna win so stop the bs'ing. Lets help the others that want to learn and keep it that way.


----------



## whitebutler

*I'm DUM*

I have two 390xp's ones a big P.O.S. and the otherr runs totaly awsome:help:


----------



## CHEVYTOWN13

*5100 Venom Glands™*

Isn't this thread about porting


----------



## super3

gink595 said:


> Sorry Parris, I just seen you on at RS this past weekend and then all the sudden it seems you had this awesome idea to use a drill chuck, IDK maybe it's silly thinking but I just assumed your awesome idea came from there. I don't know if Eric invented it, I just said that is where I seen it at his shop. As for Super3's picture I think we might have had a converstaion about that at a GTG, so IDK can't say for sure but it might have stemmed from there too. I'm sure Mike will chime in and set it straight.




Yes we did talk about that at a GTG quite a while back. I know it wasn't my brainstorm,same as a lot of threads, someone asked what was the best way to mount one and a chuck was mentioned along with many other ways. Not even sure where I was at reading it, if it was EC, thanks a million Eric.


----------



## gink595

CHEVYTOWN13 said:


> Isn't this thread about porting



Not anymore, it's about fighting:hmm3grin2orange:


----------



## gink595

super3 said:


> Yes we did talk about that at a GTG quite a while back. I know it wasn't my brainstorm,same as a lot of threads, someone asked what was the best way to mount one and a chuck was mentioned along with many other ways. Not even sure where I was at reading it, if it was EC, thanks a million Eric.



I'm glad you remember, becasue we talk about all kinds of stuff at GTG's!


----------



## TraditionalTool

CHEVYTOWN13 said:


> Isn't this thread about porting


It was until you showed up, and as usual, the world seems to spiral down the toilet. Maybe that's because of the language you always use, it seems to come from the bottom of a toilet.

Speaking for myself, I could care less about anything you do.


----------



## CHEVYTOWN13

Fool, here's the case that goes with that jug


----------



## edisto

CHEVYTOWN13 said:


> Fool, here's the case that goes with that jug



Is that Photoshop too?


----------



## logging22

What a thread.


----------



## edisto

ClayKann101 said:


> Who cares whos idea it was it looks like it works good. Tell them both Thanks and stop B****IN'



I agree...I'm going to use it regardless!


----------



## TraditionalTool

CHEVYTOWN13 said:


> here's the case that goes with that jug


BFD.

What are you gonna do, put it together and go cut a cookie?:hmm3grin2orange:

For me, and the work that I'm doing, I don't need to have the fastest chainsaw. I don't need to have it running at 16,000 rpm, and to be honest don't even need to modify the ones I use. Although I will admit that I did rebuild and lightly modified one of the saws I use mostly, it means more to me that I brought it back to life.

I can respect people that like to modify their saws and why I point out that I lightly modified my saw when I rebuilt it, because I do like to tinker with things and like to "DIY" much of what I do.

What I have a hard time accepting is your childish remarks and rude replies to people. That has always proven to show what a true @$$#O!E you really are.

More people will respect you or your work when you learn to treat them with a little respect, so I hope you will learn how to gain some people skills one day.

I have an 'ol saying..."You have to eat a lot of $#!T before you get to the @$$#O!E", and I think it's fitting for you since you really have no clue how much you will need to eat before you get there. 

When you start treating people with respect, some of them might start treating you with some. I'm not gonna hold my breath for that to happen...until then you will just be the same 'ol pinche mojado that you have shown to be.:dunno:


----------



## Outlaw5.0

And knife edging reduces flow....................


----------



## PLMCRZY

TraditionalTool said:


> BFD.
> 
> What are you gonna do, put it together and go cut a cookie?:hmm3grin2orange:
> 
> For me, and the work that I'm doing, I don't need to have the fastest chainsaw. I don't need to have it running at 16,000 rpm, and to be honest don't even need to modify the ones I use. Although I will admit that I did rebuild and lightly modified one of the saws I use mostly, it means more to me that I brought it back to life.
> 
> I can respect people that like to modify their saws and why I point out that I lightly modified my saw when I rebuilt it, because I do like to tinker with things and like to "DIY" much of what I do.
> 
> What I have a hard time accepting is your childish remarks and rude replies to people. That has always proven to show what a true @$$#O!E you really are.
> 
> More people will respect you or your work when you learn to treat them with a little respect, so I hope you will learn how to gain some people skills one day.
> 
> I have an 'ol saying..."You have to eat a lot of $#!T before you get to the @$$#O!E", and I think it's fitting for you since you really have no clue how much you will need to eat before you get there.
> 
> When you start treating people with respect, some of them might start treating you with some. I'm not gonna hold my breath for that to happen...until then you will just be the same 'ol pinche mojado that you have shown to be.:dunno:



Give him some credit, this is his "crew"


----------



## whitebutler

Hey I'm looking for a right angle TOOL to do some port work I've got two 181 cases with the 288 top ends and want to drop the barrel on one and split head on the other at 15-1 and run 110 nitro mix is it possible one runs damn fine 110 race fuel at 12-1 but I WANT MORE and I need to port the heck out of my 394 and need dual ring 2100 piston where to get one ?????:bang:


----------



## 056 kid

ClayKann101 said:


> Give him some credit, this is his "crew"



juggalos LOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOL

LMAO.


----------



## Wildman1024

056 kid said:


> juggalos LOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOL
> 
> LMAO.



What is a Juggalo??? A dead body...Well it aint really dead but it aint like anybody that you ever met before. He'll eat monopoly and SH*T out connect 4.


----------



## trackstw

great info........... needs to be sticky at the top


----------



## edisto

Outlaw5.0 said:


> And knife edging reduces flow....................



It certainly can if it produces an abrupt change in cross-sectional area because the rest of the path was not similarly widened.


----------



## CHEVYTOWN13

A room full of panochas crying:hmm3grin2orange:
 
BTW, the cylinder will have a 2 piece cabeza AND a 7900 carbumpkin2:


----------



## gink595

CHEVYTOWN13 said:


> A room full of panochas crying:hmm3grin2orange:
> 
> BTW, the cylinder will have a 2 piece cabeza AND a 7900 carbumpkin2:



I thought you were running the HT-12 on it?


----------



## Freehand

So what's with all the spanish profanity?Once I posted an Irish derivative of the short for fornicate and got me an infraction.

We get it,you're hispanic,try not to be lame about it .


----------



## parrisw

gink595 said:


> I thought you were running the HT-12 on it?



Naa, whatever Adam is doing for him.


----------



## Mastermind

parrisw said:


> naa, whatever adam is doing for him.



lol


----------



## whitebutler

THIS PORTING THING MAKES MY BRAIN HURT:drool:


----------



## Mastermind

whitebutler said:


> THIS PORTING THING MAKES MY BRAIN HURT:drool:



The porting is what hooked me on the chainsaw collecting and tinkering hobby. I've always enjoyed faster stuff, when I found out a two-stroke could be modded for more power, well it was on!!! Drag racing got too expensive, street rods are no fun after drag racing. Circle track racing was too hard on equipment. Building saws is a blast, plus I can afford it, sometimes.


----------



## whitebutler

I still need to find a good woods porter in nor cal if anyone knows of one shoot me a pm!


----------



## PLMCRZY

whitebutler said:


> THIS PORTING THING MAKES MY BRAIN HURT:drool:


 
You gotta take it in steps. I know the basics but i do not know how to change port timing and what not. I know i can widen ports. Once i get some time im going to put this 026 under the dremel. I read this whole thread several times to understand the basics lol.


----------



## Gologit

whitebutler said:


> I still need to find a good woods porter in nor cal if anyone knows of one shoot me a pm!


 
No need for a PM...give TreeSlingr a call. He builds a good work saw.


----------



## whitebutler

Gologit yer in my back yard I'm in Oroville and how close is he


----------



## Gologit

He's in Ft. Jones up by Yreka. PM him if you're interested in having him do a saw for you.


----------



## Freehand

Treeslinger will do ya right.Right in his back yard too.....


----------



## whitebutler

well the pm is out there and I hope to go to the woods with a bit more zing in my dancin partner


----------



## edisto

whitebutler said:


> well the pm is out there and I hope to go to the woods with a bit more zing in my dancin partner


 
Are you still talking about the saw, or have you started taking the little blue pills?


----------



## whitebutler

Yep, still talking about the saw and yes it sucks when she steps on my foot because I have to buy new caulks every time


----------



## pepsifreak28

*I'm still around..*

I'm still around and I'm really impressed at all you guys and all the pictures!
I haven't been able to do much on here as much as I would like.
With family problems and trying to get some land situated to build a cabin on has kept me away but I am still kicking and still chainsawing.
Keep up the good work you guys your doing great nice to see people not be afraid to experiment and tinker.


----------



## Chesterewers

*porting okay for wood cutting saws?*



pepsifreak28 said:


> That bit would be fine files even drill bits work too anything that will grind the metal.
> The jug isn't that hard of a metal the coating isn't super hard either you would be suprised how fast you can take metal down with just a round chain file.


 
Hi I have a question, is porting okay for wood cutting saws? The video by the chainsaw guy on porting when he is done he said its for competition only not wood cutting. So how much porting can be done on a work saw? Is there anything wrong with getting maximum power from the saw by porting or should it be limited to avoid any potential problems? What problems can a ported saw have and how do we avoid them? Basicly is porting okay safe to do for our wood cutting tool.


----------



## Terry Syd

Just like a car engine, you can change the valve timing (and other aspects of the engine) to do whatever the job the engine is going to be used for. Do you want to pull a trailer or do you want to drag race with it - it's the same idea.

Most guys are happy just to get a little bit more out of what they have (eg, widening the ports). However, some of us 'petrol heads' can't leave any component of the engine alone and have to tweak everything. (I just discovered another way to get a bit more flow from my strato ports, its probably only going to be worth less than 2% more power, but I can't stop myself from doing it!)


----------



## Chesterewers

Terry Syd said:


> Just like a car engine, you can change the valve timing (and other aspects of the engine) to do whatever the job the engine is going to be used for. Do you want to pull a trailer or do you want to drag race with it - it's the same idea.
> 
> Most guys are happy just to get a little bit more out of what they have (eg, widening the ports). However, some of us 'petrol heads' can't leave any component of the engine alone and have to tweak everything. (I just discovered another way to get a bit more flow from my strato ports, its probably only going to be worth less than 2% more power, but I can't stop myself from doing it!)



its a 372 xp I want it for big cuts, I have a habit of keeping the throttle wide open, so I would just like to tweak it for more torq, it seems fast enough as long as the chain is sharp,


----------



## huskydave

Well I have done a few now and this is what I think. Everyone that can tune a carb should do some kind of muffler mod and richen up the carb a bit, gut your muffler add a small 1/2" hole or slightly bigger depending on the model and retune a bit richer. If you want to start porting saws and doing other things talk to an expert with that saw. If you start playing with the port timing your saw will almost always lose low end torque and gain higher rpm on full throttle this is because it spools up quicker and starts hitting highrpms quickly, to make up for this guys start using racechains that take up to 10 hours to sharpen properly and They won't give you any of their secrets readily. The intake and exhaust ports on most saws are rough and casted just by removing the cylinder and cleaning up the casting flaws you will notice an improvement. Widening the ports will give you more power without sacrificing torque but there is a limit to how wide yo can go depending on how wide the piston is and the model of saw and the work must be chamfered into the cylinder as to not snag a ring. I started out on a cheap saw that I paid 50.00 for and then started experimenting and asking a lot of questions slowly to give the experienced guys a chance to respond.


----------



## Terry Syd

Assuming you have already done the easy stuff like widen the exhaust and intake port, then there are two other ways to increase the torque. First, is raise the compression ratio - you know, remove the gasket under the jug and reduce the squish. That will raise the torque over the entire working powerband.

The second requires some work on increasing the time/area of the transfer ports. The increased transfer flow will drop the point of maximum delivery to the cylinder (max torque) lower in the powerband. The useable powerband will be broader. However, you may only need a little bit wider, bigger is not always better. The best way to do that is to widen the transfer ports rather than raise them. That takes quality tools to do and a skilled hand to use them.

If you've never done any porting before, you might see if you can find someone that does such work and tell him what you want.


----------



## Terry Syd

As far as changing port timing, I suggest that anyone starting out to use old pistons to try changing the timing - not the jug.

You can take .5mm off the edge of the piston next to the transfer ports to see if the extra transfer time/area is the direction you want the powerband to go.

Likewise, instead of just accepting some number, say 18 degrees of blowdown, as the magic number, just trim the edge of the old piston next to the exhaust port and find your magic number. It is far more informative to take it up in steps to see how it changes your powerband. If 16 degrees gives you a nice fat powerband that gets better as you load the saw, you will probably be glad you didn't carve up the jug for 18 degrees of blowdown.

If you don't have an old piston to carve up, a new piston isn't that expensive - and it gives you an excuse to freshen up the old girl with a new piston and ring/s after you find the timing you want.


----------



## AUSSIE1

With your 372, widen the exhaust and inlet to within 1.5mm of the piston skirt, remove the base gasket, muffler mod and retune.

This will give you more torque, not loose it.

This is a good way to start out and you will be surprised how well it will run.

There is alot more you can do further down the road as you can see if needs be.


----------



## Chesterewers

AUSSIE1 said:


> Only do the roof of the exhaust and floor of the inlet.
> Leave just a very slight bevel. You don't need much.
> A large bevel acts a bit like increased timing anyway.


 
hi how is wood cutting in Australia? On porting timing inlet moved up and exhaust down how far? I was trying to stay .015 of an inch or .38mm, if I go greater than that number twice as much or more is it too much or still within parameters for a work saw?


----------



## Chesterewers

*cleaning*



TraditionalTool said:


> I'm watching and have some Qs, but more so in regard to my specific cylinder, and how to evaluate it.
> 
> I have seen others show that shape also, so that is obviously what works. In general is the concept to keep the top and bottom the same and elongate the smashed funnel shape as you show here?
> 
> Also, another thing I was wondering is that if you leave the opening top/bottom of the port the same, do you try and hollow/expand it out behind the cylinder also?
> 
> Thanks for sharing, I am one of the folks that is wanting to learn, and I appreciate the time you've taken, don't worry about your formatting of the content, the pics are fine, and just try to hit the enter key a couple times now and then, a little white space would help, but don't let that stop you from posting.
> 
> Can you offer some advice on how you would approach this cylinder?
> 
> Like how far you would take the funnel shape out to the sides, or any info like that would be helpful. What about the fins on the sides also?
> 
> Yes, yes, I know I need to clean it up with muriatic acid...
> 
> Intake:
> 
> 
> 
> 
> 
> 
> 
> Exhaust:


 
how do you clean up everything with muriatic acid?


----------



## CedarRock

Glad to see this thread again.
I have been building a 066/660 with a bunch of saws I acquired. Bought a big bore and whittled on it a little..mostly polishing and opening up the transfers. Compared to the 460 big bore this one has very large ports. Don't know how much more to open and change dimensions..I haven't seen many posts on big bore porting.


----------



## AUSSIE1

Chesterewers said:


> hi how is wood cutting in Australia? On porting timing inlet moved up and exhaust down how far? I was trying to stay .015 of an inch or .38mm, if I go greater than that number twice as much or more is it too much or still within parameters for a work saw?



We have pretty hard woods which can be testing on saws but wouldn't have it any other way.

It's exhaust up, inlet down. Timing is measured in degree's. There is a heap of threads through the search function you need to study prior to tackling porting.



CedarRock said:


> Glad to see this thread again.
> I have been building a 066/660 with a bunch of saws I acquired. Bought a big bore and whittled on it a little..mostly polishing and opening up the transfers. Compared to the 460 big bore this one has very large ports. Don't know how much more to open and change dimensions..I haven't seen many posts on big bore porting.



You can open up your port up to 65% of the bore.


----------



## timberwolf

> Originally Posted by CedarRock
> Glad to see this thread again.
> I have been building a 066/660 with a bunch of saws I acquired. Bought a big bore and whittled on it a little..mostly polishing and opening up the transfers. Compared to the 460 big bore this one has very large ports. Don't know how much more to open and change dimensions..I haven't seen many posts on big bore porting.
> 
> You can open up your port up to 65% of the bore.



On 066 you realy cant go 65% of bore on intake or exhaust width. With BB skirt is 35mm on a 56mm bore thats only 62.5% right to the skirt edge. on 660 with newer style piston skirt is only 34mm so limited to 63% to the skirt edge.


----------



## CedarRock

timberwolf said:


> On 066 you realy cant go 65% of bore on intake or exhaust width. With BB skirt is 35mm on a 56mm bore thats only 62.5% right to the skirt edge. on 660 with newer style piston skirt is only 34mm so limited to 63% to the skirt edge.


 
63%..is that total space of intake and exhaust? How far can you safely go for squish? Right now its .017 without a gasket.

" bore on intake OR exhaust " I see that now..


----------



## kmcinms

parrisw said:


> Finally made up a nice degree wheel holder today. Was getting real tired of the crappy mount I half arsed together, and it never ran true which will throw off your measurement. Here are a few pics I think its pretty self explanatory.


 
That's awesome


----------



## timberwolf

> 63%..is that total space of intake and exhaust? How far can you safely go for squish? Right now its .017 without a gasket.



63% is the width of the skirt in relationship to the diamiter of the bore.

If the skirt was wide enough 65% is a good number and can go as high as 70% on exhaust if pushing for highest performance. Intake can go even higher if the rings don't cross into it.

I don't bother running squish any amount less than 0.020 in esp on 80cc plus engines, on a smaller saws depending on the shape of the head and squish band it can be run a little less.


----------



## kmcinms

TW, what comp. ratio is good for a 50cc saw running pump gas, woods port, and a muffler mod with stock port timing? And, altered port timing?


----------



## Brian13

Might be a dumb question, but I see this in just about every porting thread and I not sure what it is referring to. So what is blowdown? I have figured out it has something to do with exhaust but that is about it. Thanks.


----------



## blsnelling

Blowdown is the time in degrees, starting when the exhaust just starts to open, until the transfers just start to open.


----------



## Brian13

Got it, makes sense now. Thanks.


----------



## Terry Syd

Brian, it allows the cylinder to 'blowdown' prior to the transfers opening. If there is still significant pressure in the cylinder the exhaust gases will blow into the transfers when they open. 

It is usually calculated in degrees, but the area of the opening is just as important (the combination is called time/area). That is why you see the porters making the exhaust port wider. It gives more area for the blowdown period.


----------



## Brian13

Ok, its starting to all make sense. Right now all the numbers still mean nothing to me, but I am getting a general idea of how it all works. There is a lot to take into consideration when porting.


----------



## parrisw

Brian13 said:


> Ok, its starting to all make sense. Right now all the numbers still mean nothing to me, but I am getting a general idea of how it all works. There is a lot to take into consideration when porting.


 
It'll start to make more sense when you do it. The hardest part is getting consistent with the degree wheel, check out my thread on making a degree wheel, your better off to buy one then make one out of paper, it will be more accurate, and get one that's at least 7".


----------



## gink595

Brian13 said:


> Ok, its starting to all make sense. Right now all the numbers still mean nothing to me, but I am getting a general idea of how it all works. There is a lot to take into consideration when porting.


 

Like parris said it will make alot more sense when you physically degree one. Alot of guys will talk total duration numbers, to me that doesn't really matter. I use port openings to make sense of it. Now when I hear a exhaust is at 80* I know that the exhaust has been raised considerable, but if you were to tell me the exhaust is at 200* duration that doesn't really make it that clear on how high the exhaust is. Whatever works for someone I guess but total duration numbers are just some thing I have to reduce mathematically to get the info I really need. But it does sounds fancier:msp_biggrin:


----------



## parrisw

gink595 said:


> Like parris said it will make alot more sense when you physically degree one. Alot of guys will talk total duration numbers, to me that doesn't really matter. I use port openings to make sense of it. Now when I hear a exhaust is at 80* I know that the exhaust has been raised considerable, but if you were to tell me the exhaust is at 200* duration that doesn't really make it that clear on how high the exhaust is. Whatever works for someone I guess but total duration numbers are just some thing I have to reduce mathematically to get the info I really need. But it does sounds fancier:msp_biggrin:


 
Ya, what he said! I work with both numbers Frank, I feel that it allows me to be more accurate and easily check my work back and fourth. Like if ex is at 160°duration, I know it should be 100°Atdc, so I'll find TDC then check opening and if I get 100° I know I'm bang on.


----------



## Brian13

A degree wheel is on my list of things to get. One thing that I noticed when looking at them is they all seem to only go to 90* and count back down to 0*. Thats what I am looking for right?


----------



## gink595

Summit Racing SUM-G1057 - Summit Racing® Cam Degree Wheels - Overview - SummitRacing.com


----------



## tlandrum

gink595 said:


> Summit Racing SUM-G1057 - Summit Racing® Cam Degree Wheels - Overview - SummitRacing.com


 
thats the one i have too


----------



## Brian13

Thanks, its on the way.


----------



## parrisw

Here is an idea if you have access to a lathe you can do it up nice. 

And ya Frank I know of others that do it too! LOL


----------



## Brian13

I saw that, and I like that!! Looks real nice, but I dont have access to a lathe. Me and my dad have been looking for a small one used, so we can have another piece of equipment that we really dont need LOL.


----------



## parrisw

Brian13 said:


> I saw that, and I like that!! Looks real nice, but I dont have access to a lathe. Me and my dad have been looking for a small one used, so we can have another piece of equipment that we really dont need LOL.


 
Maybe you can find someone to do it for ya, its literally like a 2 min job to put a lip on the chuck so the degree wheel fits nicely.


----------



## Brian13

I will have to look into that for sure. Looking at the pics it looks pretty simple, just have to see if I can find somebody around here with a lathe.


----------



## blsnelling

Where's the best place to pick up a chuck?


----------



## tlandrum

lowes or home depot usually have the keyless chuck


----------



## blsnelling

tlandrum2002 said:


> lowes or home depot usually have the keyless chuck


 
$25, LINK.


----------



## parrisw

blsnelling said:


> Where's the best place to pick up a chuck?



Any place that sells tools, its doesn't even need to be keyless, mine isn't and I can get it plenty tight enough.



Brian13 said:


> I will have to look into that for sure. Looking at the pics it looks pretty simple, just have to see if I can find somebody around here with a lathe.


 
Yep its easy. I'd do it for you guys, but would cost a few bucks to ship them out.


----------



## Brian13

I was thinking last night( not always my strong point), for those of us with no easy access to a lathe could you just use a large flat washer to sandwich the degree wheel to the chuck? Seems plausible but I dont have a chuck in front of me just yet. I am going to see if my dad has any dead drills that I can steal a chuck from. He has enough stuff I should be able to find something laying around.


----------



## gink595

Brian13 said:


> I was thinking last night( not always my strong point), for those of us with no easy access to a lathe could you just use a large flat washer to sandwich the degree wheel to the chuck? Seems plausible but I dont have a chuck in front of me just yet. I am going to see if my dad has any dead drills that I can steal a chuck from. He has enough stuff I should be able to find something laying around.


 
If you buy the summit wheel it comes with the adapters and you won't have to worry about it. Just find a chuck and the metric bolt and your good to go.


----------



## Mastermind

Brian13 said:


> I was thinking last night( not always my strong point), for those of us with no easy access to a lathe could you just use a large flat washer to sandwich the degree wheel to the chuck? Seems plausible but I dont have a chuck in front of me just yet. I am going to see if my dad has any dead drills that I can steal a chuck from. He has enough stuff I should be able to find something laying around.


 
Yes that would work, just make sure it is centered properly. I've got the degree wheel mounted many different ways, a person is only limited by their imagination when it comes to these things. I still use a printed degree wheel on thick card stock. I do make it larger than I did when I started, but I get repeatable results with no problems.


----------



## Brian13

Good deal, I ordered the Summit wheel last night. I have a Husky 55 jug I am going to practice grinding on and then I will move on to my 044/046:msp_smile:.


----------



## parrisw

Brian13 said:


> I was thinking last night( not always my strong point), for those of us with no easy access to a lathe could you just use a large flat washer to sandwich the degree wheel to the chuck? Seems plausible but I dont have a chuck in front of me just yet. I am going to see if my dad has any dead drills that I can steal a chuck from. He has enough stuff I should be able to find something laying around.


 


gink595 said:


> If you buy the summit wheel it comes with the adapters and you won't have to worry about it. Just find a chuck and the metric bolt and your good to go.


 
Yep. Like Frank said they come with different adapters, mine had a couple but they all had a slight amount of play, so why no do it on the lathe and get it perfect. Also here is a tip for you guys. Use a automotive drain plug for your bolt, that's what I did they have a big flanged head on them for the sealing surface and you don't have to use a big washer, looks much better.

As you can see in this pic. Its a very standard thread. I think it might of been 1/2 20


----------



## Blowncrewcab

parrisw said:


>


 
What is that Blue thing Mounted back by the Handle??


----------



## parrisw

Blowncrewcab said:


> What is that Blue thing Mounted back by the Handle??


 
Its the ignition coil. Its a 2 piece ignition on a 288xp


----------



## tbone75

great info guys thanks!!!


----------



## Mag460

Lot of good info on porting.. I have a stihl460 I have muffler mud done to it an I have question about porting.. I was thinking of taking base gasket out.. Then cleaning up intake cast marks for better flow.. Now on piston the transfer slots what do u do with them? Also for exhaust port I was gana do little wider an like 1 mm higher.. Would tht be good since I'll be running no base gasket? An for top an bottom of ports they should have little roundness to them an straight sides correct? An keep all intake ports same just make transfer clean an knife edges right?


----------



## tlandrum

you need to do some more searching. your plan sounds like a disaster in the works. dont ever go into a saw and raise or lower anything without using a degree wheel to see where your at and map out where your going.


----------



## Chesterewers

tlandrum said:


> you need to do some more searching. your plan sounds like a disaster in the works. dont ever go into a saw and raise or lower anything without using a degree wheel to see where your at and map out where your going.



Just make the exhaust wider, you can widen intake too, like they say map it out mark it so you don't go too wide, and don't raise or lower the intake exhaust unless you really don't care, it might lose rpm or compression if you mess up, someone on here said they messed up and used JB weld to fix it with success, but the saw he used was either cheap or free, I forget. Anyway another easy way for added power is just to port the muffler. The old stihls 066 076 ect have huge ports no porting needed on those mufflers. Thats before the EPA got all crazy on a little engine. Why not regulate huge polluters, try regulating 3rd world countries to save the air and weather. If you ever been to any where the air is so dark you can't see 1000 yards away very clearly you know what I am talking about buses spew out black diesel, a small engine in the Forrest is a joke, aren't trees healthy from carbon monoxide in amounts able to be used? Anyway sorry for long post, the owner of this site can delete it if they get sick of me.


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## Mag460

Ok ill forget making higher or lower.. I was told u could mill it 1mm higher an be good.. An I only taking base gasket out after I check the squish. To get more compression. An of course I'll measure piston skirts an leave the appropriate thicknesses an for rings. On exhaust could u go 1 to 2mm wider depending what I aloud after I measure, could u go wider where muffler bolts on?


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## parrisw

Mag460 said:


> Ok ill forget making higher or lower.. I was told u could mill it 1mm higher an be good.. An I only taking base gasket out after I check the squish. To get more compression. An of course I'll measure piston skirts an leave the appropriate thicknesses an for rings. On exhaust could u go 1 to 2mm wider depending what I aloud after I measure, could u go wider where muffler bolts on?



Put the piston on with no rings. Bolt the cylinder on with a couple of bolts, get a very fine point pencil so you can get right out to the edges of the port, and mark the port sides on the piston, oh degrease the piston first so the pencil will take. Now take the cylinder off and measure from the pencil line to the edge of the piston skirt, how much you got? Now widen to .100" to the skirt edge. I would also make sure that the total port width after doesn't exceed 65% of bore width. When you widen, make the sides of the port vertical, and blend it out and up to the roof of the ex port without raising it.


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## half_full

Wow, I just made it through all 23 pages of this thread. 15 and 16 were skipable...
I have been playing with a "can't lose" (big scratch, low comp.) P&C for my 372 and found a few things I did wrong. Oh well. Still be interesting to see if or how it runs and learn.

So, in the few threads I've read through I see to polish exhaust and leave intake alone or rough cut it only. Why is this?


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## sun64

There are probably better people on this site that can explain it better than me but here goes.
With a polished exhaust port, there is less drag from the escaping gasses on the sides etc which will lead to less back pressure and faster gas removal out the muffler.

With a semi course intake port, if it is slightly rough the fuel leaving the carbie will spray onto the intake faces and be picked up by the incoming air charge. It will lead to a better air/ fuel mixture in the crank case.
If you highly polished ther inlet port , the fuel would have a tendancy to run off the polished sides and into the crank case and will not have mixed properly for the next charge into the combustion chamber.
It is better to leave them slightly rough but without any casting flaws, lips etc 
Hope this helps


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## vals poeticus

*hi all*

hi..im vals from jakarta an two stroke lover,would you all mind what is the first you want to do to build a drag two stroke,i ve kawasaki ninja 150 cc and yamaha 135 rx king both are two stroke,all i want to know is how to port,polis,cyilender etc count,i read the many books and i dont understand till now:hmm3grin2orange::hmm3grin2orange:,if you can help me in the very simple languange...tennkyouuu alll!!!


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## Hddnis

vals poeticus said:


> hi..im vals from jakarta an two stroke lover,would you all mind what is the first you want to do to build a drag two stroke,i ve kawasaki ninja 150 cc and yamaha 135 rx king both are two stroke,all i want to know is how to port,polis,cyilender etc count,i read the many books and i dont understand till now:hmm3grin2orange::hmm3grin2orange:,if you can help me in the very simple languange...tennkyouuu alll!!!








Mr. HE


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## Mastermind

Hddnis said:


> Mr. HE



The art of trolling....... :msp_rolleyes:


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## thunder saw

hi kinda new here. was wondering if im on the right track with my exhaust port. still need to smooth it out some. thanks.


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## shorthunter

Few pictures of my Sachs-Dolmar 143. The transfer ports were a PITA, everything else went as planned (for the most part). I also ported the intake to smooth the transfer between the carb and cylinder and I port matched the muffler to the cylinder and opened the exit port about 30%. Maybe I can get a video of the saw running in the next day or two


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## shorthunter

Video of the 143. This was the 9th or 10th test cut after the rebuild. You will notice that the saw starts to run out of fuel 3/4 of the way through the cut. 34" bar spinning .404 chain, 7 tooth sprocket


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## Mastermind

The port work you have done here have not made enough difference to run the saw out of fuel. You have other stuff going on.


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## shorthunter

That was the 9th or 10th cut on the first tank of fuel, not counting the run time when I did the first few startups. The tank was dry when I pulled the cap


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## Mastermind

Oh......I see what you mean.


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## blsnelling

For starters, it's tuned considerably too rich. Did you put a kit in the carb? Check the fuel line? Tank vent clogged?


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## Mastermind

I didn't watch the video. He didn't do anything I could see that would make any improvement in the saw's performance.


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## shorthunter

I had it running rich for the first tank of fuel. I will retune the carb next time I get the saw out. Did a pretty mild port job. Finished product ended up about 3.6 mm wider on the exhaust port. Can't remember the other numbers off the top of my head. Very little change in timing, increased transfer volume and knocked the edges off the back of the transfer port wall Figured this would help give beginners an idea of where to start


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## shorthunter

I was pretty limited in what I could do with this saw without replacing the stock muffler and intake but I wanted to give it a little boost in performance through increased efficiency. If you have suggestions feel free to share


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## mdavlee

The muffler needs to be opened up and then see where the intake and exhaust ports open.


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## shorthunter

good advice mdavlee, that is where I started the process. The way these old Dolmar mufflers are constructed it limits what you can do. Maybe I can get a picture up later. The intake is even more limiting on the 143 but I don't want to pull the intake off just to take a picture


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## LegDeLimber

She sounded leaner after the chain catch at the 1:31 mark.


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## shorthunter

Couple more cuts with the carb tuned a little closer. Still running a 33" Carlton bar with .404 chain, 7 tooth sprocket.


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## HusqyStihl

I understand this is an old thread but if anyone has any trashed jugs i would love to experiment and ease into porting or even just smoothing out before i rip into my good jugs. Usually i work with alot of Stihl 029's, 039's 290's, 390's, Husq 51, 55, 261, 262xp, 36, 350, 455, 372.... Hell, i'll take any kinda junked jugs to mess around with if at all possible. Just for continued education and a little experience.... TIA

~Moose


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## Chris-PA

HusqyStihl said:


> I understand this is an old thread but if anyone has any trashed jugs i would love to experiment and ease into porting or even just smoothing out before i rip into my good jugs. Usually i work with alot of Stihl 029's, 039's 290's, 390's, Husq 51, 55, 261, 262xp, 36, 350, 455, 372.... Hell, i'll take any kinda junked jugs to mess around with if at all possible. Just for continued education and a little experience.... TIA
> 
> ~Moose


I think you be best off getting an entire cheap saw to mess with, although probably something with pro construction (I port clamshells but I'm nuts). Something like an Earthquake or any of the Chinese RedMax clones. Then you can play as much as you want and not risk damaging anything valuable. And if you trash the jug you can get another cheap on eBay and try again. Best is that if you get it right you'll actually have a good tool when you are done.

You could start with a used "good" saw, but parts will be expensive and you'll still be hesitant to try stuff.


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## huskihl

Chris-PA said:


> I think you be best off getting an entire cheap saw to mess with, although probably something with pro construction (I port clamshells but I'm nuts). Something like an Earthquake or any of the Chinese RedMax clones. Then you can play as much as you want and not risk damaging anything valuable. And if you trash the jug you can get another cheap on eBay and try again. Best is that if you get it right you'll actually have a good tool when you are done.
> 
> You could start with a used "good" saw, but parts will be expensive and you'll still be hesitant to try stuff.


Or find the cheapest replacement cylinders on ebay and buy that saw. My jred 625 has a ported huztl 272xp cylinder on it and runs much stronger than when it was a 625. For $30 I didn't care if I killed it. I milled with it last week and it was "acceptable". 
Some cylinder kits are cheaper yet.
Not personal experience, but I wouldn't go less expensive than huztl. Reports of poor quality go way up after that


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## HusqyStihl

Ive got a couple 290 runners but doubt id wanna port them at first attempt. Maybe if i had some junk jugs to give it a shot first... Maybe ill find some. I do have some recently blown 390 A/M tops. Maybe ill screw with them


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## huskihl

HusqyStihl said:


> Ive got a couple 290 runners but doubt id wanna port them at first attempt. Maybe if i had some junk jugs to give it a shot first... Maybe ill find some. I do have some recently blown 390 A/M tops. Maybe ill screw with them


My ms310/039 was my 2nd port job. Oem timing was rather aggressive Imo for a plastic saw. Exhaust was at 160° duration before I started. I widened the exhaust and intake to within 1.5mm of the skirt and lowered the intake some. Took that saw and a stock 039 to the pile (both were timed before the mods and we're identical) and I gained about 15%. A few holes in the muffler and enlarging the hole in the deflector are a must.


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## kwhite87

BUMP


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## husqvarna addict

Hello I need some opinions on intake port duration. I have an older dirt bike cylinder that I am going to add boyesen ports to it to increase fuel and air into the transfers area and it has reeds on this model. I am wondering if I could add the boyesen ports to a chainsaw piston port cylinder or would it just spit air and fuel back out the carburetor? Has anyone attempted this on a chainsaw, hope to hear back thanks.


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## Way2Slow

Looking for a place to ask this and here looks like a good place.
What do ya'll use to do transfer ports in these small cylinders? I have C.C. Specialties 1MC and 3MC right angle heads I use on boat motors but these are too large for the transfer ports in a 48mm MS360 port I'm wanting to do.
I'm retired now and basically gotten out of the porting business and really don't care to buy their 300AMC @ $400 just to do one or two cylinders for one chain saw. Years back I bought a small pneumatic right angle grinder when they first came out for $100 to play with but that cheap thing broke fairly quickly and I see they are wanting $300 for those now.

I see a lot of people doing porting on here and figure they all can't be in the business with these high dollar tools I've been using and there must be something cheaper that will work for a few cylinders.

I'm new on here and have been doing a ton of searches on a good port map for the MS360 and I've seen several things I have noticed people doing on these cylinders I've never found advantageous to do.
The biggest thing is making the port window in the cylinder larger than the runner going to it. I've seen this on almost every intake port I've seen for this cylinder. My experience has always shown when you have an area that increases in size before the charge inters the cylinder, it lets the charge slow down and fuel separate. This will cause a decrease in torque and will cause large droplets of gas to enter the cylinder that do not burn as well, causing a decrease in power. I have always found it better to have a one or two degree taper into the cylinder with at least a straight runner going to it. No increases in volume anywhere. That and an 80 grit texture on the surface just to create just enough turbulence to keep the fuel suspended in air stream. Never polish and intake runner that has fuel going through it, that does bad things.

Another thing is indiscriminate hogging. Every flake of metal you remove should serve a specific purpose, to increase airflow/velocity. What looks good to the eye might not look worth a darn to the air passing through it. The higher the rpm, the more porting may be required, but a work two stroke will not need same amount of metal removed as a completion/race two stroke and you want to leave as much as possible to get keep the crankcase volume to a minimum. Sometimes to the point of actually going in with epoxy and fillers to reduce the volume. Sometimes on a 10,000 rpm boat motor, I've cut and epoxied enough they don't even look like the same motor inside but on the same motor to pull a skier with, I may do very little grinding, just in some key areas to improve velocity.


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## weimedog

Way2Slow said:


> Looking for a place to ask this and here looks like a good place.
> What do ya'll use to do transfer ports in these small cylinders? I have C.C. Specialties 1MC and 3MC right angle heads I use on boat motors but these are too large for the transfer ports in a 48mm MS360 port I'm wanting to do.
> I'm retired now and basically gotten out of the porting business and really don't care to buy their 300AMC @ $400 just to do one or two cylinders for one chain saw. Years back I bought a small pneumatic right angle grinder when they first came out for $100 to play with but that cheap thing broke fairly quickly and I see they are wanting $300 for those now.
> 
> I see a lot of people doing porting on here and figure they all can't be in the business with these high dollar tools I've been using and there must be something cheaper that will work for a few cylinders.
> 
> I'm new on here and have been doing a ton of searches on a good port map for the MS360 and I've seen several things I have noticed people doing on these cylinders I've never found advantageous to do.
> The biggest thing is making the port window in the cylinder larger than the runner going to it. I've seen this on almost every intake port I've seen for this cylinder. My experience has always shown when you have an area that increases in size before the charge inters the cylinder, it lets the charge slow down and fuel separate. This will cause a decrease in torque and will cause large droplets of gas to enter the cylinder that do not burn as well, causing a decrease in power. I have always found it better to have a one or two degree taper into the cylinder with at least a straight runner going to it. No increases in volume anywhere. That and an 80 grit texture on the surface just to create just enough turbulence to keep the fuel suspended in air stream. Never polish and intake runner that has fuel going through it, that does bad things.
> 
> Another thing is indiscriminate hogging. Every flake of metal you remove should serve a specific purpose, to increase airflow/velocity. What looks good to the eye might not look worth a darn to the air passing through it. The higher the rpm, the more porting may be required, but a work two stroke will not need same amount of metal removed as a completion/race two stroke and you want to leave as much as possible to get keep the crankcase volume to a minimum. Sometimes to the point of actually going in with epoxy and fillers to reduce the volume. Sometimes on a 10,000 rpm boat motor, I've cut and epoxied enough they don't even look like the same motor inside but on the same motor to pull a skier with, I may do very little grinding, just in some key areas to improve velocity.



Careful.... One thing you will learn after a few years here is...there is more complexity and technology required in porting these one cylinder wonders than a Yamaha TZ750! Certainly more than those lowly 300plus HP tweaked Mercs!

Next.....if you aren't from Ohio or the PNW you probably have the wrong DNA... your going just have to work twice as hard...

last? Why port an saw? Just buy an Echo cs590?


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## Chris-PA

weimedog said:


> last? Why port an saw? Just buy an Echo cs590?


'cause 9k rpm is boring?


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## husqvarna addict

I need some opinions on intake port duration. I have an older dirt bike cylinder that I am going to add boyesen ports to it to increase fuel and air into the transfers area and it has reeds on this model. I am wondering if I could add the boyesen ports to a chainsaw piston port cylinder or would it just spit air and fuel back out the carburetor? Has anyone attempted this on a chainsaw, hope to hear back thanks.


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## weimedog

Chris-PA said:


> 'cause 9k rpm is boring?


Like just turn in that screw on the carb? That will get you past 9k! Then punch a screw driver through the muffler to let that mean machine breath!


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## Way2Slow

Nope I'm not a yankee so I guess I'm banned from the sight. I'm just a grumpy old southern redneck, born and raised in GA. Other than the near 23 years playing GI Joe for Uncle Sam and living all over the place, I've lived in GA my whole life.

Why a chainsaw, I found it laying in the woods and appeared to have been there at least a year. It was frozen up so it had to be torn down and new crank and bearings installed. Going back together, I'm like Tim Allen in Tool Man, it's gotta have more power. I don't thing I've ever built a stock anything in my life, so why start now. I've owned chainsaws since the mid 60's but this is the first one I've had to tear down. I started off with twin Mac-10's on my go cart in the early 60's. Then got into racing outboards in the late 60's and have owned high performance cars and raced cars most of my life so I got into cylinder heads at an early age also. Needless to say, I've spent a few hours with a die grinder. Too many actually, the doctors claim the vibration from them is what caused all the problems I'm having with my hands now and not even supposed to be using one.


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## Way2Slow

I hope that was not a question for me about dirt bikes. I know less about those than I do chainsaws. I've never rode or worked on those. Don't even know what a boyesen port is. I know what boyesen reeds are but you have to have a reed valve engine to use those.


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## weimedog

Way2Slow said:


> Nope I'm not a yankee so I guess I'm banned from the sight. I'm just a grumpy old southern redneck, born and raised in GA. Other than the near 23 years playing GI Joe for Uncle Sam and living all over the place, I've lived in GA my whole life.
> 
> Why a chainsaw, I found it laying in the woods and appeared to have been there at least a year. It was frozen up so it had to be torn down and new crank and bearings installed. Going back together, I'm like Tim Allen in Tool Man, it's gotta have more power. I don't thing I've ever built a stock anything in my life, so why start now. I've owned chainsaws since the mid 60's but this is the first one I've had to tear down. I started off with twin Mac-10's on my go cart in the early 60's. Then got into racing outboards in the late 60's and have owned high performance cars and raced cars most of my life so I got into cylinder heads at an early age also. Needless to say, I've spent a few hours with a die grinder. Too many actually, the doctors claim the vibration from them is what caused all the problems I'm having with my hands now and not even supposed to be using one.



Sounds like a lot of us got here from somewhere else...TRYING to retire! Have land in Alabama that might be a destination. Have to sell out of here first. Chainsaw & building rock walls is how I fed my racing habit as a kid. Dirt bikes & motocross until my 40's didn't leave me with much for joints. SO moved to saws as my motorsport because I can't ride as I want to. AND we cut a lot here on the farm. Pay taxes selling timber, heat with wood, fence & trail maintenance. The folks here are much less testosterone enhanced than the racing crowd therefore easier to deal with...a lot of really good folks here. instead of bragging about the 10k motor and 5k suspension, its about a 350 port job. Maybe a 1000 dollar saw with a 350 dollar port job! Much more down to earth here. And unlike the racing many here work with their saws and the hobby is an extension of their livelihood. Even though the costs are low, the financial risk can be much much higher..

And as a person who's family is from the south, but raised in the north; spend years traveling the country & even international I can tell you "Red Neck" starts around Syracuse and ends in California to the west, and south to Florida. You fit right in. Any questions....look at those maps of red and blue by county, not state; of this election. If its red....


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## Way2Slow

Just my luck. Finished putting saw together and stuck in a stump I left a little tall the other day from two dead pines I took down in my yard. I didn't go three inches and sparks flew big time. Every tooth on a brand new chain looks like someone spent five minutes with a side grinder on the cutting edge of them. Totally wiped that sucker out. I made a few attempts at cuts just to load the saw and see how it would do, and it's running great. Sharpen the chain and try the other stump tomorrow, or go get one of the logs I hauled off, maybe I can see how it cuts then.

Had my neighbor go with me to some 30" logs we took out of my yard a couple months ago so he could run it and I tuned the carb. Then we made about a dozen cuts with the 20" bar buried the whole time and it just ripped through them and never slowed up. He commented "man! that thing is fast and light". When I put him out at his house, I told him not to forget "his" saw. I told him merry Christmas and gave it to him. 
He has a small business doing yard work and trees, and someone stole his saw a month ago out of his truck and was going to cost him almost a grand to replace it. He does a lot for me and keeps my grass cut, (which I do a lot for him keeping his ragged equipment going) so I figured he would get way more use out of it than me. I will say, my 029 super couldn't hold a candle to it.


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## volvo2før

Anyone tried chamfering the piston skirt like this? I know a 2-stroke motorcycle guru that do this on almost every engine he's porting.


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## LegDeLimber

I expect that you'd need to factor in, just how much that big ramp shape, affects the intake timing.

Also curious if it might let the oil film slip into the piston to cylinder clearance, a pinch better.


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## Chris-PA

volvo2før said:


> Anyone tried chamfering the piston skirt like this? I know a 2-stroke motorcycle guru that do this on almost every engine he's porting.


The only effect I can see of that would be to increase intake duration. You'd have to watch out for free porting the exhaust too.


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## blsnelling

I don't see the advantage. I want the port to open as quick as possible, allowing the max flow with the max case pressure.


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## volvo2før

Chris-PA said:


> The only effect I can see of that would be to increase intake duration. You'd have to watch out for free porting the exhaust too.


I think the advantage will be to let more oil remain on the cylinder wall, specially on the upper area. Better oil coating also improves the seal between the rings and bore wall and decrease compression leakage.


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## Chris-PA

volvo2før said:


> I think the advantage will be to let more oil remain on the cylinder wall, specially on the upper area. Better oil coating also improves the seal between the rings and bore wall and decrease compression leakage.


How will it do that? Most pistons already have a small bevel, and oil films are pretty thin.


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## volvo2før

Chris-PA said:


> How will it do that? Most pistons already have a small bevel, and oil films are pretty thin.


Many pistons also don't have any bevel at all. The square edge of the skirt will scrape oil off the cylinder wall instead of letting it settle. When chamfering the skirt, the rings can also carry lubricant to the upper cylinder area. I know there have been much smoother idling when chamfering pistons with only one pistonring. I will surely give it a try on my next port job ☺


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## Stihl311

New to this forum been cutting for a little while and just got a ms 311 was wanting to port and polish and muffler mod it and tune the carb by someone who knows what there doing....wondering if after the woek is done would I gain much horsepower or enough to run a 24" .050???? My buddy has a 391 and he runs a 24 inch bar and the hp's are so close I am wondering if this mod will allow me to run that size bar no problem with a full chisel chain


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## shorthunter

Most people here will tell you not to waste your time with porting on a plastic crankcase saw. 

The muffler mod will help if you trim the limiter tabs and retune the carb


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## Chris-PA

Porting on a clamshell isn't any different except it's a bit further to reach inside due to the extended cylinder, and it is harder to increase compression by cutting the cylinder. The plastic case isn't going to break due to the power increase.


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## millpro

I have a husqvarna 257. Doing a complete rebuild. It had scored the piston. The cylinder which is what came on it new was fine with the exception of a nick at the bottom of the exhaust window. I have ported it and took the nick out. It wasn't bad but I'm wondering if I went to far. I have ring coverage at bottom dead center. Just wondering if it's enough???


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## blsnelling

millpro said:


> I have a husqvarna 257. Doing a complete rebuild. It had scored the piston. The cylinder which is what came on it new was fine with the exception of a nick at the bottom of the exhaust window. I have ported it and took the nick out. It wasn't bad but I'm wondering if I went to far. I have ring coverage at bottom dead center. Just wondering if it's enough???


BDC isn't what matters. Is the skirt fully covered at TDC?


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## millpro

blsnelling said:


> BDC isn't what matters. Is the skirt fully.


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## millpro

blsnelling said:


> BDC isn't what matters. Is the skirt fully covered at TDC?


Yes its git plenty of skirt below the window.


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## millpro

Alright I got the 257 ported out. I had to port the top of the exhaust window a tad more than I was comfortable with because when the ring and piston scored it nicked the top of the exhaust port so o had to at least clean that up. The whole time I'm thinking if I screw it up I'll just pop a 262 p/c on it and be done. I also opened up the intake and hogged out the intake spacer. Squish was at .030. I was wanting .020 but I will live with it. Got home this evening and got it all buttoned up and it started right up.


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## millpro

Trying to download a video but it keeps telling me it's to large even though I've shortened it to 20 sec. Oh well anyways the 257 ported is hitting a real good lick and has great throttle response. Brad I honed it just a tad to get some good cross hatch and my compression is around 140# I have .030 squish . What should I expect to see once this thing breaks in a bit. 150 to 160???


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