# 361 Shootout



## timberwolf (Nov 16, 2010)

Have 2 361s and a 361BB on hand so thinking of comparing muffler mods along this line and also the BB vs factory cylinder and piston.

Hope to get some dyno and flow bench numbers as well.


----------



## wiskey_6 (Nov 16, 2010)

This should be good to sit back an watch.


----------



## RTK (Nov 16, 2010)

cool


----------



## timberwolf (Nov 16, 2010)

One thing with the 361 filter is the whole exhaust gets pushed through one small hole in the funnel shaped piece of junk that was pulled out. Very restrictive and a lot of changes in direction and shape of flow.


----------



## Trigger-Time (Nov 16, 2010)

Thanks TW, Am very glad to here this 

I am on my 2nd 361 and it's just now getting broken in.
I saved my 361 MM muffler from 1st 361 and was planing
on doing some testing my self to see if my MM really made
any difference or an I just making more noise.
I have the new muffler to switch out with this one.

But from things you have said I need to remove the muffler guts. correct?











TT


----------



## timberwolf (Nov 16, 2010)

Your muffler mod will be getting past some of the restriction but the flow will still need to pass through the basket at the inlet of the muffler so there is some potential restriction.


----------



## Trigger-Time (Nov 16, 2010)

timberwolf said:


> Your muffler mod will be getting past some of the restriction but the flow will still need to pass through the basket at the inlet of the muffler so there is some potential restriction.



I was surprised that very little exhaust now comes out of the org port.

Also I guess it's on my end but your pic show up as *X*
TT


----------



## timberwolf (Nov 16, 2010)

Not sure why the pics are not comming up for you, they are linked from here on post #60.

http://arboristsite.com/showthread.php?t=154490&page=4

If you look at that junk in the muffler It is pretty clear why the flow would rather go out the side than around through the inner passages.


----------



## 2000ssm6 (Nov 16, 2010)

All the MM I've done on 361s turn them into another saw. Those have got to be in the top 5 of "most choked up saws". I bet they gain a bit more w/o the internals.


----------



## mtngun (Nov 16, 2010)

I love it when you post a project TW. Love your hard data and your logical approach.


----------



## Tzed250 (Nov 16, 2010)

Now this will be a good thread...


----------



## SawTroll (Nov 16, 2010)

timberwolf said:


> Your muffler mod will be getting past some of the restriction but the flow will still need to pass through the basket at the inlet of the muffler so there is some potential restriction.



I remember that Andy used to say that the basket had enough (and large enough) holes to not matter, but I always was a bit sceptical about that.

It is a pity that you probably can't include a stock Euro 361 into your test, but I look forward to the results anyway!


----------



## blsnelling (Nov 16, 2010)

Andy frowned on about anything that wasn't stock or OEM.


----------



## madhatte (Nov 16, 2010)

I also always wondered about the assertion that those holes were "enough". The angles don't look right to me. I am looking forward to the results of this test.


----------



## SawTroll (Nov 16, 2010)

blsnelling said:


> Andy frowned on about anything that wasn't stock or OEM.




Hmmm - why did he mod 361 mufflers then, and be very public about it?

He also used to talk about modding the muffler of the "strangled" US 260s, to compensate for the power loss.


----------



## parrisw (Nov 16, 2010)

OOO, a TW thread!! cool. Here is the pics. See if I can help here. 

Question for ya TW, are you tig welding your mufflers? Last time I did a muffler was the first time with my new tig, and I had a hell of a time cause the filler was too thick, couldn't find any thinner. So I haven't tried it yet but was going to try to use some mig wire as filler since its sooo much smaller. What do you use?


----------



## Gypo Logger (Nov 17, 2010)

parrisw said:


> OOO, a TW thread!! cool. Here is the pics. See if I can help here.
> 
> Question for ya TW, are you tig welding your mufflers? Last time I did a muffler was the first time with my new tig, and I had a hell of a time cause the filler was too thick, couldn't find any thinner. So I haven't tried it yet but was going to try to use some mig wire as filler since its sooo much smaller. What do you use?



No pics yet that I can see. TW great work, but couldn't you have had the common decency to have showcased a Husky! Lol
John


----------



## parrisw (Nov 17, 2010)

Yukonsawman said:


> No pics yet that I can see. TW great work, but couldn't you have had the common decentcy to have showcased a Husky! Lol
> John



Working for me John. Not sure what's up.


----------



## Gypo Logger (Nov 17, 2010)

parrisw said:


> Working for me John. Not sure what's up.


 Maybe Mntgun can come to the rescue, he's good with this sort of thing, but I can't rule out my computer, although other pics are showing fine.
John


----------



## parrisw (Nov 17, 2010)

Yukonsawman said:


> Maybe Mntgun can come to the rescue, he's good with this sort of thing, but I can't rule out my computer, although other pics are showing fine.
> John



Hmm, 

anybody else having problems seeing the pics?


----------



## SawTroll (Nov 17, 2010)

Yukonsawman said:


> No pics yet that I can see. ....



I can't see them either, but then I am at a cell-phone dial-up at the cottage at the moment!


----------



## SawTroll (Nov 17, 2010)

No.


----------



## gemniii (Nov 17, 2010)

I tried quoting the text, in the edit box grabbed one of the img url's, dropped that into my navigation and it prompted me to log in, then they all showed up.

Edit - I just repeated it in IE, the pics didn't show up, I went thru the process.
The lines in the image point to like:





http://arboristsite.com/attachment.php?attachmentid=158236&d=1289956375
instead of 




http://www.arboristsite.com//attachment.php?attachmentid=158236&d=1289956375
note no www in the first one

I think you have to log into a different server - http://arboristsite.com/, instead of http://www.arboristsite.com/

/edit - for japanese try http://www.arboristsite.com//attachment.php?attachmentid=158236&d=1289956375


----------



## SawTroll (Nov 17, 2010)

Looks just fine!


----------



## gemniii (Nov 17, 2010)

Ok I put www in front of the links, can you see em now?

If so I'll delete some of the others.



parrisw said:


> OOO, a TW thread!! cool. Here is the pics. See if I can help here.
> 
> Question for ya TW, are you tig welding your mufflers? Last time I did a muffler was the first time with my new tig, and I had a hell of a time cause the filler was too thick, couldn't find any thinner. So I haven't tried it yet but was going to try to use some mig wire as filler since its sooo much smaller. What do you use?


----------



## Tohya (Nov 17, 2010)

All of the images show up for me.


----------



## parrisw (Nov 17, 2010)

Its always worked for me? So don't know what's up.


----------



## timberwolf (Nov 17, 2010)

> Question for ya TW, are you tig welding your mufflers? Last time I did a muffler was the first time with my new tig, and I had a hell of a time cause the filler was too thick, couldn't find any thinner.



Got to give away all the secrets eh!

I have not been able to source filler less than 1/16 up here, there is at least one place in US selling thinner and specilty fillers but it was going to be pretty expensive to get them shipped up and through customs. I had planned to put an order together but had not got to it yet.

1/16 is a bit thick, I can make do with it on mufflers but on pipes it makes a big weld, Here is my redneck engineering solution, mig filler is too floppy to deal with on it's own but twisting two 0.023 wires together with a drill makes it stiffer and it works quite nice.






I don't know what was up with the pics last night, first off I posted in the wrong thread by accident then either my computer or the site was slow and I had some failed uploads when trying to fix the problems.


----------



## tdi-rick (Nov 17, 2010)

Subscribed


----------



## Trigger-Time (Nov 17, 2010)

Last night I could not see TW pictures, TW poasted a link to the the org
post where he had pictures. I still couldn't see pictures but noticed that 
I wasn't logged in on that thread  So I logged in as I had it open
in a new window. Then I could see pictures in both threads. I'm at work
now, I had to do the same thing at work as I did at home to see the pictures.


TT


----------



## willbarryrec (Nov 17, 2010)

*Thanks in advance TimberWolf!*

Looking forward to the thread!

My 361 is still stock,maybe this thread is what will get me cutting and drilling.

I was even more interested after seeing this. 




2000ssm6 said:


> All the MM I've done on 361s turn them into another saw. Those have got to be in the top 5 of "most choked up saws". I bet they gain a bit more w/o the internals.


----------



## Gypo Logger (Nov 17, 2010)

gemniii said:


> Ok I put www in front of the links, can you see em now?
> 
> If so I'll delete some of the others.



Works for me now, thanks gemniii.
I like the look of the finished muffler. Good job Brian.
John


----------



## blsnelling (Nov 17, 2010)

Any of these getting one of those beautiful side swept pipes? I'd still love to have me one of those! Just make it for a 440 with a 460 topend:rockn:


----------



## timberwolf (Nov 17, 2010)

Nope, no pipes for these. Plan will be for a standard woods ported 361, a fairly hot woods ported 361 with more work on the intake, piston and carb. With the BB I want to take it about as hot as I can and keep it as a true work saw for myself. It may get a welded piston if I can't get enough compression from the BB head and a workover on the carb and intake as well.


----------



## blsnelling (Nov 17, 2010)

Sounds like fun!


----------



## ttyR2 (Nov 17, 2010)

I've used thick MIG wire (which is still thin compared to straight welding rod) for TIG work in the past. Just cut it off into usable lengths and straighten it.


----------



## parrisw (Nov 17, 2010)

timberwolf said:


> Got to give away all the secrets eh!
> 
> I have not been able to source filler less than 1/16 up here, there is at least one place in US selling thinner and specilty fillers but it was going to be pretty expensive to get them shipped up and through customs. I had planned to put an order together but had not got to it yet.
> 
> ...



Great thanks Brian! I brought home some .023 stuff, so I'll wind it together. That's an awesome idea. I too can't get anything smaller then 1/16, and it just wasn't working for me.

What kind of typical carb work do you do for a woods port, I have not ventured there yet. Would just smoothing out the ridge help? Or do you have to bore the whole thing and make bigger butterflies?


----------



## timberwolf (Nov 17, 2010)

I tried that but found it hard to get nice and straight which made it hard to control. Mind you I was working with 0.023 wire, bigger mig wire might be ok. Not much luck either with single .030 stainless mig wire as it was just too springy to straighten well.

For the basic woods port I would just clean up the ventury and a few rough points. for the others I plan on some lathe work and the BB may get new flutterbys.


----------



## gemniii (Nov 17, 2010)

Trigger-Time said:


> Last night I could not see TW pictures, TW poasted a link to the the org
> post where he had pictures. I still couldn't see pictures but noticed that
> I wasn't logged in on that thread  So I logged in as I had it open
> in a new window. Then I could see pictures in both threads. I'm at work
> ...


Apparently there are two english sites and a japanese site that gets used.

Examples:
http://www.arboristsite.com/ - is the english site I normally link into.


http://arboristsite.com/ - where some peeps login - NO www


http://new.arboristsite.com/ where I get japanese characters

If you noticed when TW said where he posted the pictures it was 
http://arboristsite.com/showthread.php?t=154490&page=4

so watch your prefixes.


----------



## Trigger-Time (Nov 17, 2010)

gemniii said:


> Apparently there are two english sites and a japanese site that gets used.
> 
> Examples:
> http://www.arboristsite.com/ - is the english site I normally link into.
> ...



Hmmmm..............I always log onto http://www.arboristsite.com as thats how it is in my favorites.


Thanks,
TT


----------



## Eric Modell (Nov 17, 2010)

First muffler mod. How do you open up the muffler to gut the restrictions inside.

Thanks eric


----------



## Trigger-Time (Nov 17, 2010)

Eric Modell said:


> First muffler mod. How do you open up the muffler to gut the restrictions inside.
> 
> Thanks eric



Noy trying to take anything away from TW's thread.


You can see in this thread how to pull muffler apart.
http://www.arboristsite.com/showthread.php?t=33528

But TW may have a better way as TW's looks a little more neat
after it's opened.


TT


----------



## timberwolf (Nov 17, 2010)

I found it not bad just to roll the crimp open with these. The mufflers on other models with welded seams though need to be cut and rewelded.


----------



## Eric Modell (Nov 17, 2010)

Thanks trigger-time for the link. I can see where a 361 needs to be opened up.


----------



## Eric Modell (Nov 17, 2010)

Cool timberwolf i have a pair of nippers a little larger then yours but I think I can make the tool work.


----------



## MS390 (Nov 18, 2010)

wiskey_6 said:


> This should be good to sit back an watch.



Amen.....


----------



## Thorcw (Nov 18, 2010)

Im watching


----------



## timberwolf (Nov 18, 2010)

I'll try to get some stuff posted tonight, lost most of last night to a hunting related diversion.


----------



## Carlyle (Nov 18, 2010)

I am always ready for a race. Guess that I will have to watch this thread, seems I might have some interest. Thanks for your hardwork TW. Not doubting the BB but I hope the standard woods port Stihl rocks.

Carlyle


----------



## timberwolf (Nov 18, 2010)

They will all rock, no question, just the standard one will rock longer if pushed really hard. Though there will be a little speed trade off in smaller wood. I plan to push the limits a bit with the BB as it can always be detuned a bit if need be and I will keep a close eye on it for signs of heat or excessive piston/ring wear.


----------



## MS390 (Nov 18, 2010)

*muffler assembling*

muffler assembling: weld,brass or just bend the thin iron back??


----------



## blsnelling (Nov 18, 2010)

It'll help keep this thread clean and readable if we refrain from quoting the pictures You can quote a post, and then delete the images.


----------



## MS390 (Nov 18, 2010)

blsnelling said:


> It'll help keep this thread clean and readable if we refrain from quoting the pictures You can quote a post, and then delete the images.



it´s a deal


----------



## timberwolf (Nov 18, 2010)

TX brad, the pics were getting a bit much, not sure if it was just th way I posted them first or a server thing.

Anyway, For the crimp if it is folded open it closes back up fairly well. Getting the basket and junk out is a pain even once the muffler is open.

I am not big on brass for muffler work. Brass really is best for tight fit joints and not ideal when mixed with steel and elevated temperatures. My beef with brass is the nightmare it is to try to weld anything after a brass joint fails.


----------



## blsnelling (Nov 18, 2010)

MS390 said:


> it´s a deal



Thanks for not taking it personal Just a friendly reminder and suggestion.


----------



## MS390 (Nov 18, 2010)

blsnelling said:


> Thanks for not taking it personal Just a friendly reminder and suggestion.



I know


----------



## Zombiechopper (Nov 18, 2010)

Brian, can you post a port map of your finished porting layout? I ported the heck out of my 361 and I'm still not getting what I think I should be able to out of it. I'm hoping I can learn something from what yours will look like. I widened inake and exhaust as much as skirts allow and swept the intake side transfers way in to the intake. Opened the lower transfer windows and widened the bottom transfers a bit. Squish is at .018. It runs great, but it doesn't explode out of the gate like I think it could. I'm wondering if the carb is holding it back because I have the low needle all the way out from the seat...like three turns. So far out that opening farther doesn't affect it. I went back and worked the transfers a little more and that helped but I'm curious if I need to change the carb now


----------



## blsnelling (Nov 18, 2010)

Zombiechopper said:


> Brian, can you post a port map of your finished porting layout? I ported the heck out of my 361 and I'm still not getting what I think I should be able to out of it. I'm hoping I can learn something from what yours will look like. I widened inake and exhaust as much as skirts allow and swept the intake side transfers way in to the intake. Opened the lower transfer windows and widened the bottom transfers a bit. Squish is at .018. It runs great, but it doesn't explode out of the gate like I think it could. I'm wondering if the carb is holding it back because I have the low needle all the way out from the seat...like three turns. So far out that opening farther doesn't affect it. I went back and worked the transfers a little more and that helped but I'm curious if I need to change the carb now



I put a Zama C3M on my MS361.


----------



## Zombiechopper (Nov 18, 2010)

blsnelling said:


> I put a Zama C3M on my MS361.



Is that for a 440/044 Brad? Did you _need_ it to deliver enough fuel or were you just trying it out? Also, any linkage changes needed to swap that carb?


I get plenty of high speed jet but I suspect the lack of enough low is hampering throttle response and how fast it returns to idle


----------



## blsnelling (Nov 18, 2010)

Zombiechopper said:


> Is that for a 440/044 Brad? Did you _need_ it to deliver enough fuel or were you just trying it out? Also, any linkage changes needed to swap that carb?
> 
> 
> I get plenty of high speed jet but I suspect the lack of enough low is hampering throttle response and how fast it returns to idle



I just wanted the larger venturi. You should have good throttle response with the stock carb. I have heard mention of some carb issues on the 361. Maybe you need a new carb.


----------



## timberwolf (Nov 18, 2010)

Not bad at all stock. But the torque is weak and it would not take much pushing to drop RPM.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/xTJioQ1QAFg?hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/xTJioQ1QAFg?hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## gink595 (Nov 18, 2010)

parrisw said:


> OOO, a TW thread!! cool. Here is the pics. See if I can help here.
> 
> Question for ya TW, are you tig welding your mufflers? Last time I did a muffler was the first time with my new tig, and I had a hell of a time cause the filler was too thick, couldn't find any thinner. So I haven't tried it yet but was going to try to use some mig wire as filler since its sooo much smaller. What do you use?



You should be able to weld thin gage with .060 filler, I have some .040 filler, but actually perfer to use .060 on 22 ga. I can turn the amperage up a bit and run a little faster than if I turn it down and use a smaller filler. Same with tungsten, I found it easier to weld with a larger diameter tungsten on light gage than to go with a smaller tungsten. I know it sounds crazy but try it, you can get more heat in faster to start your puddle and then you can go like hell rather than trying to drive the heat in the material and then go slow with the puddle.


----------



## Tzed250 (Nov 18, 2010)

gink595 said:


> You should be able to weld thin gage with .060 filler, I have some .040 filler, but actually perfer to use .060 on 22 ga. I can turn the amperage up a bit and run a little faster than if I turn it down and use a smaller filler. Same with tungsten, I found it easier to weld with a larger diameter tungsten on light gage than to go with a smaller tungsten. I know it sounds crazy but try it, you can get more heat in faster to start your puddle and then you can go like hell rather than trying to drive the heat in the material and then go slow with the puddle.





Is that how you will do it when you build the pipe for my 660???


.


----------



## gink595 (Nov 18, 2010)

Yes


----------



## timberwolf (Nov 18, 2010)

Gink, you right about it going faster with the 1/16, I just found I was able to keep the welds smaller and put in less heat with lighter filler, also on the pipes ended up with smooter finnish on insides. I have tried the .040 tungsten, did not like it and went back to 1/16 but grind a fairly fine point. But all that is just learning by doing so no saying if it is right or wrong.

Here are a few pics of doing another muffler from the start.

I find it best to open the crimp on the 3 sides opposite the outlet as they are easiest to close back up. 4 spot welds to grind out then pull the screen and the basket is gone. Restristion is 8.75mm so only about 0.09 square inches.


----------



## timberwolf (Nov 18, 2010)

Compression was between about 165 or a little more and 175 or a little less on all three saws, have not checked the BB yet but will put it together stock eventually.

All three saws were new and 1 was lean from factory.


----------



## RTK (Nov 18, 2010)

That lean plug picture sure looks lean, either that or it is brand new


----------



## timberwolf (Nov 18, 2010)

Plug had been run for a few min then saw shut off right out of full load cut. 

Anyway off to look at some differences between the 361 Stihl and BB jugs. Something interesting with the transfers. Stihl jug has transfer ducts that measure about 5.8mm x 19.2mm, BB Jug has ducts 4.1mm x 17.2mm. Works out that big bore has only about 63% of the transfer duct area. 

Wonder if that will show up on the dyno and in the wood. Got a feeling that this is going to hurt the top end.












5mm bolt for scale, BB on left, Stihl jug on right.


----------



## Trigger-Time (Nov 18, 2010)

timberwolf said:


> Compression was between about 165 or a little more and 175 or a little less on all three saws, have not checked the BB yet but will put it together stock eventually.
> 
> All three saws were new and 1 was lean from factory.



Seems most 361 have good compression.

I do take it 361 in video muffler was stock not just the motor.

Am really looking forward to you finding out what the best 
size of sq in of muffler opening is for stock saw. I'm looking for the
smallest sq in that gets the cherry of the gains. 

361 muffler I posted pictures of was on my first 361 the gills 
added .140 sq in. I had a little trouble with idle on that saw
but it idles and runs good on the new 361. I kind of think
it was the carb on first. It would seem like I had it, cut with it
set it down and it would die.

TT


----------



## Outlaw5.0 (Nov 18, 2010)

Seems all big bores have small transfers. My first gen 460BB had larger transfers than my 2nd gen 460BB.


----------



## timberwolf (Nov 18, 2010)

Upper transfers are pretty close, BB has a bit more angle going into the cylinder but size wise very close.

The lowers end up small I think on many BB's because there is not a lot of room to clear the flywheel on that side and case on PTO side, then the bore eats up 1mm extra on each side.






Head volumes came in about 6.1cc to 6.4cc with squish between 0.31 and 0.35 so the three saws stock all spec out very close.


----------



## parrisw (Nov 18, 2010)

gink595 said:


> You should be able to weld thin gage with .060 filler, I have some .040 filler, but actually perfer to use .060 on 22 ga. I can turn the amperage up a bit and run a little faster than if I turn it down and use a smaller filler. Same with tungsten, I found it easier to weld with a larger diameter tungsten on light gage than to go with a smaller tungsten. I know it sounds crazy but try it, you can get more heat in faster to start your puddle and then you can go like hell rather than trying to drive the heat in the material and then go slow with the puddle.



Ya, I don't know, I tried to go faster, and just kept blowing through the muffler, I just couldn't get it to melt the filler properly, the dang muffler would just melt before the filler would.


----------



## timberwolf (Nov 18, 2010)

I know exactly what you are saying there. When the filler is thicker than the base metal it is not like the book that says you make the puddle then stick the filler into it. I find it starts to be a bit more of running the arc from the puddle up onto the filler as you move forward and push the filler in. What say you Gink would that be a fair description?


----------



## parrisw (Nov 18, 2010)

timberwolf said:


> I know exactly what you are saying there. When the filler is thicker than the base metal it is not like the book that says you make the puddle then stick the filler into it. I find it starts to be a bit more of running the arc from the puddle up onto the filler as you move forward and push the filler in. What say you Gink would that be a fair description?



Ya, I hear ya! Frustrating to say the least!! Why not just use smaller filler, way easier.


----------



## Zombiechopper (Nov 18, 2010)

try makin a ring of spot welds. Then put the fill rod away and just concentrate on pushin the puddle.


----------



## angelo c (Nov 18, 2010)

timberwolf said:


> Got to give away all the secrets eh!
> 
> 1/16 is a bit thick, I can make do with it on mufflers but on pipes it makes a big weld, Here is my redneck engineering solution, mig filler is too floppy to deal with on it's own but twisting two 0.023 wires together with a drill makes it stiffer and it works quite nice.



TW, check out these twist pliers, made to safety wire parts on airplanes. should make your .023 wire braiding much easier.

http://www.amazon.com/Amazing-Safety-Wire-Twisting-Pliers/dp/B0000AXB5T


----------



## timberwolf (Nov 18, 2010)

I make the twisted pairs ~50 feet at a time, run single strand out and back anchor it on the far end then clip it to chuck of hand drill, hold some tenssion and pull the trigger. Takes but a few seconds.


----------



## parrisw (Nov 18, 2010)

angelo c said:


> TW, check out these twist pliers, made to safety wire parts on airplanes. should make your .023 wire braiding much easier.
> 
> http://www.amazon.com/Amazing-Safety-Wire-Twisting-Pliers/dp/B0000AXB5T



Problem with those it you can't do a really long section of wire with them, like you need for filler material. I'm sure the drill works just fine.


----------



## AUSSIE1 (Nov 19, 2010)

The aftermarket kits I've seen have had smaller transfers particularly the uppers.
Inside the 372 BB's lowers can be opened up with little work to match the opposite side. The OEM is no different here.


----------



## gink595 (Nov 19, 2010)

parrisw said:


> Ya, I don't know, I tried to go faster, and just kept blowing through the muffler, I just couldn't get it to melt the filler properly, the dang muffler would just melt before the filler would.






timberwolf said:


> I know exactly what you are saying there. When the filler is thicker than the base metal it is not like the book that says you make the puddle then stick the filler into it. I find it starts to be a bit more of running the arc from the puddle up onto the filler as you move forward and push the filler in. What say you Gink would that be a fair description?



Hard to say, there is alot of variables to consider, experience, amperage, technique, type of filler rod and where you direct your arc. Also how the joint is prepared. I can do it fine with .060 filler, thats not to say I won't get a blow through here and there but that is typically due to inconsistent joint gaps, once I get started and get in the ryhthm of dipping the filler I can typically go for as long as I can feed the filler rod.

TW I do the same with concentrating on welding the puddle and filler rod and not worry about putting heat in the base metal, especially on thin 22-24 gage. When I start my weld I make a tack and almost a bridge just joining the two sides (butt joints) I then work the tack weld and add filler to that. I watch what I call the keyhole, the area in front of that weld, if I see that area creating a "hole" I will either back off the pedal and pull the tungsten back over the weld and then put my filler in that hole and then direct the arc over that area to fill the keyhole, just a back and forth motion. This is difficult to explain in text, not sure it makes much sense to anyone but me


----------



## Trigger-Time (Nov 19, 2010)

It may be here and I missed it, but what is the sq inches
of stock cylinder exhaust port?





TT


----------



## timberwolf (Nov 20, 2010)

Stock exhaust port area (flat plane) is .563 in2 so that make the muffler restriction about 16% of the port area.

I'll get some port maps up later.


----------



## timberwolf (Nov 20, 2010)

Here are the stock port maps.

BB is wider on intake and exhaust, but lacking on transfers, also I don't like the shape of BB transfers much and they are not very even side to side.


----------



## timberwolf (Nov 20, 2010)

Durrations then are:

*361BB*
E 156.4
T 108.6 to 115.4
I 140.6

*361 Stihl*
E 160.6
T 109.6 to 113.6
I 149.6


----------



## mtngun (Nov 20, 2010)

Thanks as always for the hard data, TW. 

If I may pick your brain a little -- and I'll understand if you don't want to reveal all your knowledge -- I assume, based on some of the HP charts you have posted in previous threads, that you are using MOTA, which I recently obtained and will soon be playing with. How do you determine the correct ignition timing numbers that MOTA requires? 

I haven't figured out how to hook a timing light and degree wheel and then still be able to start the darned thing, not to mention the degree wheel prolly wouldn't appreciate being spun 13,000 rpm.


----------



## timberwolf (Nov 20, 2010)

I have timed saws off fly wheel from idle to WOT and found that none of the saws I looked at had *any* fancy timing advance curves. So I just use the book spec, what ever it is 23 or 26 BTDC. Mota does not show a big difference with changes to timing, not sure it is 100% accurate in that aspect. Also, as I don't mess much with ignition timing on work saws it really does not matter much for the software.

Couple muffler pics. For this on just one 3/4 in pipe and will open up the existing outlet a little more.


----------



## Trigger-Time (Nov 20, 2010)

timberwolf said:


> Couple muffler pics.
> 
> For this on just one 3/4 in pipe and will open up the existing outlet a little more.




Nice bead!

With my 8th grade math I come up with, the 3/4 pipe is about 72% of the
exhaust port.......is this correct?

I apologies for such a simple question, but I do want to know.


Thanks
TT


----------



## timberwolf (Nov 20, 2010)

That sounds about right but there is a good .20 in2 in the back so should take it up to about 110% or so. It took quite a bit of ajustment on the low speed and a little on th HS to bring it back to tune. Running about 15,000 RPM now.

Cutting about 2.3 seconds which works out to a 22% improvment over stock.

Sorry, video is dark, was getting late.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/PIDbIq5nrkw?hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/PIDbIq5nrkw?hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## timberwolf (Nov 20, 2010)

Caps off for a trim, top cap trimmed, bottom still has limiter tab.


----------



## mtngun (Nov 20, 2010)

Thanks for the timing info, TW. The lack of advance makes sense, since saws run WOT all the time.


----------



## Zombiechopper (Nov 20, 2010)

Well I got mine tuned up pretty well with the stock carb today. I got it tuned nice with 2.5 out on the low and good reliable idle and good restarts. I'm really curious if the carb is holding this saw back? Brian, am I way out to lunch needing that much low jet?


----------



## timberwolf (Nov 20, 2010)

On this stock saw with MM I am out exactly 1 3/4. 

We'll see just how nuch the carb is holding it back.


----------



## timberwolf (Nov 20, 2010)

By the computers numbers the stock 361 was just over 4.3 hp @ 10000 and MM was 5.1 hp likely just slightly higher peek HP RPM if I ran a longer calculation with closer RPM intervals it would show. But this matches pretty well with the in the wood gain. More torque right across and it was easy to feel the difference.


----------



## mtngun (Nov 20, 2010)

timberwolf said:


> By the computers numbers the stock 361 was just over 4.3 hp @ 10000 and MM was 5.1 hp likely just slightly higher peek


Thanks for the MOTA data, TW. 19% gain in power just by a MM, pretty impressive. Or a reflection on how bad the stock muffler is ?

I'm surprised it's making peak torque at a mere 6500 rpm, but then it has pretty sane port timing numbers.


----------



## Zombiechopper (Nov 21, 2010)

TW, do you plan on tweaking the venturi, boring out, or a carb swap? Or does it depend on what you find? I really think I have a carb issue with how mine is ported. Timing is all stock but seriously wide ports and fairly aggressive transfers. Squish at .018 with no popup. It has quite good throttle response but not as good as my ported 460 nor as good as a stock 200T so I think it needs something more. It also revs up to about 13k real quick then takes a couple of seconds and bursts to 15500. Four strokes nice there but the funny lag and jump to rev out is unlike other saws I have.


----------



## gemniii (Nov 21, 2010)

timberwolf said:


> By the computers numbers the stock 361 was just over 4.3 hp @ 10000 and MM was 5.1 hp likely just slightly higher peek HP RPM if I ran a longer calculation with closer RPM intervals it would show. But this matches pretty well with the in the wood gain. More torque right across and it was easy to feel the difference.



Finally NUMBERS that look like they could be repeated!

Now do you have anything like that in a 660 w/ regular muffler and the same 660 w/ DP muffler like at https://www.baileysonline.com/itemdetail.asp?item=QS+1122+140+0800&catID=1981 ? Just wishing 

Thanks TW for your work.


----------



## timberwolf (Nov 21, 2010)

Here are some predictions for the 361s.

Bottom set is the stock, second up standard work port, next up hot work port with more carb and intake work and higher compression and top set BB taken about as far as I figure I can and keep it a work saw.






Something to keep in mind with software design though is it does not look at some things like flame speed friction or piston/component mass nor does it easily look at fuel delivery curve and that results in seeing some values out at high RPM that won't be seen in real life. These saws won't cut at 12-13k in the wood though looking at the graphs it would be easy to think they should.


----------



## timberwolf (Nov 21, 2010)

I have all sorts of numbers for 066s and 660s, in general a muffler mod takes them from just over 7 hp to about 7.7 hp with DP cover and a little over 8 if opening them right up.

New 660 produced in last year or two are not ported as well factory as the older 660s and 066s. They produces same peek HP but at a slightly higher RPM, the torque peek though is not as high or wide. Trouble is exhaust durration is up around 180 deg or a little more stock. One thing for sure is you don't want to raise the exhaust port further when porting these as work saws.


----------



## timberwolf (Nov 21, 2010)

Torque is dotted line, hp solid.

So at opperating RPM looking at more what it does in the 9500-11,500 range.


----------



## 2000ssm6 (Nov 21, 2010)

That dyno graph is awesome, takes alot of CAD to build one of those.

Opps, not a dyno. Intresting none the less.


----------



## timberwolf (Nov 21, 2010)

These are just computer models, have not pulled the dyno out yet. It will show different numbers, just the way they work, you won't see the real high RPM stuff like with software as the real dyno with bar and chain accelerating a weight is affected by friction, flame speed limits ect.

Few more pics

Dual port muffler for either BB or the hotter 361
Side by side of 361 and 361 BB pistons 
Stock transfer ports and then them being done, piston ring is pushed in with piston to help keep them even along the top edge.


----------



## mtngun (Nov 21, 2010)

Yes, MOTA does make it look like the modded saws would cut at 12,000+. I look forward to the results with your dyno.






Stock 361 transfers.





Ported 361 transfers.


----------



## parrisw (Nov 21, 2010)

Really nice work!! You never cease to amaze me at all. 

Question, on a typical work saw how much do you taper the transfers back towards the intake side? Is just a couple MM fine here? I usually don't go too overboard here.


----------



## timberwolf (Nov 21, 2010)

It very much depends on the saw and the build just how much to take the transfers back. On the stihls like 066 the ring end pins limit how far back. On the 4 port designs it is easier to keep them lower and wider. In general it is better to go wider before going higher as it gives a longer blowdown. On this one I kept the transfers almost stock height by the time the jug gets lowered. And went back about 1mm on the front and 3mm on the rear.

Nothing wild on the porting here, just a solid fast worksaw. Exhaust was raised only about .5mm intake lowered about 1mm and the ports taken out to full width. Fair bit of work on the transfers to improve flow.


----------



## parrisw (Nov 21, 2010)

timberwolf said:


> It very much depends on the saw and the build just how much to take the transfers back. On the stihls like 066 the ring end pins limit how far back. On the 4 port designs it is easier to keep them lower and wider. In general it is better to go wider before going higher as it gives a longer blowdown. On this one I kept the transfers almost stock height by the time the jug gets lowered. And went back about 1mm on the front and 3mm on the rear.
> 
> Nothing wild on the porting here, just a solid fast worksaw. Exhaust was raised only about .5mm intake lowered about 1mm and the ports taken out to full width. Fair bit of work on the transfers to improve flow.



Really nice looking port work!!!

Thanks. Most of the saws I do are Husky's, 372's 395's ect. Those are my fav's. All of my saws get the cylinders machined, sometimes do a popup as well. Usually works out well that I can raise the ex back up to get a little more blowdown. I think I raised the transfers on the last 372 to get them at 120° with a final blowdown of 20°, but that was a while ago so I'm not totally sure. Can't remember how far I tapered the transfers back, I think probably a few mm.


----------



## timberwolf (Nov 21, 2010)

About 20 deg blowdown is about the least I would go on the 4 port huskies, any less and they start to feel weak on the top end. 2 port stihls with tighter bases can go a little less than 20 deg if built for torque but not much less. Looking at about 23 deg blowdown on this one.


----------



## banshee67 (Nov 21, 2010)

i dont want to hijack, but i also dont want to start a whole new thread about something to dumb;

what are those 2 plastic rectangular shaped things that snap into the underside of the clutch cover by the bar studs?
i lost one while cleaning the other day, do they serve any purpose? it seems like they are there for the chain to glide across, sort of like a chain slide on a 4 wheeler/dirtbike , but how would the chain even get so far out of line to even come in contact with them in the first place? should i even bother replacing it?


----------



## parrisw (Nov 21, 2010)

timberwolf said:


> About 20 deg blowdown is about the least I would go on the 4 port huskies, any less and they start to feel weak on the top end. 2 port stihls with tighter bases can go a little less than 20 deg if built for torque but not much less. Looking at about 23 deg blowdown on this one.



Wow! Ok, thanks. 

On the Last 395 I did, it was all I could do to get 20°, I didn't raise the transfers at all, but raised the ex up some. Do you think I'm ok to raise the ex up some more on this 395 to get more blowdown? I think I had it at 160° dur. Compression is at 195psi now.

Thanks for the tips. Sorry though, don't want to clutter up your thread too much.


----------



## timberwolf (Nov 21, 2010)

On that sized saw I think you could raise the exhaust a bit, compression is up there at 195 and it will likely get stronger at the top of the powerband if you can find a little more area in the top of the exhaust port. Sometime it does not take much to give it enough blowdown so that cylinder pressure drops below base pressure when the transfers open.


----------



## parrisw (Nov 21, 2010)

timberwolf said:


> On that sized saw I think you could raise the exhaust a bit, compression is up there at 195 and it will likely get stronger at the top of the powerband if you can find a little more area in the top of the exhaust port. Sometime it does not take much to give it enough blowdown so that cylinder pressure drops below base pressure when the transfers open.



Great thanks allot for the tips!


----------



## timberwolf (Nov 21, 2010)

Turned down the base and made a popup piston for it.

Videos on doing that stuff here if you haven't watched it before.

http://www.youtube.com/watch?v=t3Q6OsmMXEU
http://www.youtube.com/watch?v=oyuhi12zlp8

It cutting about 2 seconds flat now, I feel it should be a bit better, so going to run a tank of gas through it and see where the compression settles.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/ytajFzFAEbY?hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/ytajFzFAEbY?hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## parrisw (Nov 21, 2010)

timberwolf said:


> Turned down the base and made a popup piston for it.
> 
> Videos on doing that stuff here if you haven't watched it before.
> 
> ...



DAM!! That's really awesome! 

What's the chain on it? Anything special?


----------



## timberwolf (Nov 21, 2010)

Just factory chain, not super sharp either.

Compression at 195 psi.

I richened it up a hair and made another few cuts, cutting in the mid 1.8 range now.


----------



## parrisw (Nov 21, 2010)

timberwolf said:


> Just factory chain, not super sharp either.
> 
> Compression at 195 psi.
> 
> I richened it up a hair and made another few cuts, cutting in the mid 1.8 range now.



Nice! Looks like the same compression tester that I have.


----------



## MS390 (Nov 21, 2010)

*carb*

1. What to do?? 

2.How many RPM does your saw run?

TW...... :yourock:


----------



## timberwolf (Nov 21, 2010)

On this carb I just took out the venturri 1mm and cleaned up some rough edges on the carb and the intake. 15k RPM or a hair less WOT no load seems about where it cuts best. 

E 160.0 deg
T 116.6 deg
I 156.4 deg


----------



## Metals406 (Nov 21, 2010)

Brian, what elevation are you at? There should be a 3% modifier per 1,000 feet of elevation for comp.


----------



## timberwolf (Nov 21, 2010)

Just a few hundred feet here so I don't bother counting that.


----------



## Metals406 (Nov 21, 2010)

timberwolf said:


> Just a few hundred feet here so I don't bother counting that.



I was just curious. . . So that's be around 185 here for me. A guy would have to be mindful building a 200+ comp engine here, and then shipping it to sea level.


----------



## parrisw (Nov 21, 2010)

timberwolf said:


> On this carb I just took out the venturri 1mm and cleaned up some rough edges on the carb and the intake. 15k RPM or a hair less WOT no load seems about where it cuts best.
> 
> E 160.0 deg
> T 116.6 deg
> I 156.4 deg



Do you do your carb work on a lathe or by hand?


----------



## Anthony_Va. (Nov 21, 2010)

The gains are easy to see TW. Looks like you have got her purring. 

I enjoyed the vids on the pop-up and base turning also. I've learned a load watching this thread so far. Appreciate it buddy!


----------



## timberwolf (Nov 22, 2010)

Thanks guys, its fun.

This carb was just done by hand, likely the other two carbs will get a more involved work over.


----------



## Zombiechopper (Nov 22, 2010)

timberwolf said:


> Thanks guys, its fun.
> 
> This carb was just done by hand, likely the other two carbs will get a more involved work over.



If its not a trade secret kind of thing, could you describe how you work a carb over by hand? This is kind of a mystery to me. I'm picturing sandpaper on a dowel to open the diameter and smoothing the edges of the venturi?


----------



## timberwolf (Nov 22, 2010)

I just use a small cutter and work the edge of the venturi down, measure here and there to keep it even, then smooth it out. 361 carbs are quite smooth to start, but some of the carbs are pretty rough in the venturri. 

cleaning up the carb is one of the small things that on its own likely not even a measurable a change, but combine a few of these details and and it adds up.


----------



## parrisw (Nov 22, 2010)

timberwolf said:


> Thanks guys, its fun.
> 
> This carb was just done by hand, likely the other two carbs will get a more involved work over.



So, you didn't open up where the butterfly sits? Just the venturi?


----------



## timberwolf (Nov 22, 2010)

Just the venturi. To open it up where the butterfly sits you would need to do it on lathe and use a larger butterfly. It can get tricky with internal passages and the LS orifices near the throttle plate.


----------



## parrisw (Nov 22, 2010)

timberwolf said:


> Just the venturi. To open it up where the butterfly sits you would need to do it on lathe and use a larger butterfly. It can get tricky with internal passages and the LS orifices near the throttle plate.



Ya, I've been wanting to try to bore a carb on my lathe. Was going to do my 371. I have a few throttle plates around that are slightly larger that would work.


----------



## timberwolf (Nov 22, 2010)

The lathe work is the easy part, making that big of a change to the shape of the carb will throw the fuel curve way off and the carb will likely need some internal tweaking to get it running right esp for a work saw that needs to start, idle, accelerate, cut at different RPMs and return to idle without reving or stalling.


----------



## Trigger-Time (Nov 24, 2010)

Bump


----------



## MS390 (Nov 25, 2010)

timberwolf said:


> The lathe work is the easy part, making that big of a change to the shape of the carb will throw the fuel curve way off and the carb will likely need some internal tweaking to get it running right esp for a work saw that needs to start, idle, accelerate, cut at different RPMs and return to idle without reving or stalling.




???? lathe work,any pics..... I´m lost


----------



## mtngun (Nov 25, 2010)

MS390 said:


> ???? lathe work,any pics..... I´m lost


TW has posted pics of lathe work on other threads. For example see his 460/660 build thread on the Saw Building 101 forum. The machine work is routine, nothing unique to the 361.

http://www.arboristsite.com/showthread.php?t=83777&highlight=


----------



## MS390 (Nov 25, 2010)

mtngun said:


> TW has posted pics of lathe work on other threads. For example see his 460/660 build thread on the Saw Building 101 forum. The machine work is routine, nothing unique to the 361.
> 
> http://www.arboristsite.com/showthread.php?t=83777&highlight=



thanks alot mate


----------



## timberwolf (Nov 25, 2010)

I'll try to dig out dyno and flow bench tonight, just had a mess of deer and broken ATV taking up some shop space. 

When I get to the carb work for the other 361's I'l get some pics of that stuff posted too.


----------



## MS390 (Nov 25, 2010)

*youre the man!!!!*



timberwolf said:


> I'll try to dig out dyno and flow bench tonight, just had a mess of deer and broken ATV taking up some shop space.
> 
> When I get to the carb work for the other 361's I'l get some pics of that stuff posted too.



thanks


----------



## timberwolf (Nov 25, 2010)

I did get a dyno run done tonight for a stock 361, but still going over the data, upgraded firmware on data logger and it caused some glitches... I'll figure it out.


<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/1SlpLPpo8zg?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/1SlpLPpo8zg?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>


----------



## mtngun (Nov 25, 2010)

Good to see you using that dyno, after all the trouble it took to make it.


----------



## Cornfed (Nov 25, 2010)

timberwolf said:


> I did get a dyno run done tonight for a stock 361, but still going over the data, upgraded firmware on data logger and it caused some glitches... I'll figure it out.
> 
> 
> <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/1SlpLPpo8zg?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/1SlpLPpo8zg?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>



Maybe a dumb question, but where does one buy a saw dyno?


----------



## mtngun (Nov 26, 2010)

Most saw dynos are homemade. There is an outfit or two selling small engine dynos, but they are way out of my price range.


----------



## timberwolf (Nov 26, 2010)

Anything ready to use is going to start in the $4-5k range and on top of that will need custom gearing and mounting setups to connect a saw to it. I have well over $2500 in mine and that was making a lot of the parts myself and going cheep on the data aquisition end. I think I am going to end up scraping the data unit and software and go to something else, could never get it to run as advertised and their tech support just danced around. Last firmware was supposed to fix it but does not look like it did, plus caused other issues. Oh well...there goes a grand.


Here are a couple different systems.

http://inertiadyno.com/inertia-dyno/inertia-dyno-models-by-stan-hewitt-2010/

http://www.land-and-sea.com/kart-dyno/kart-dyno-price.htm


----------



## mtngun (Nov 26, 2010)

Sorry to hear about the data acquisition headache, TW. I admire the craftsman ship of your dyno, and imagine the programming must have been interesting, too.

If I ever win the lottery and have the time and money, I'd like to build a dyno, but I was thinking of an old fashioned brake dyno. All you'd need for instrumentation is a tach (already have that, or easy to make a spindle tach) and some sort of force transducer, which could be as simple or as fancy as you wanted. Data collection could be done manually if necessary, though a simple PC data aq would be better. The brake itself would be more challenging. but I was thinking to try an automotive disc brake. Dunno if it could handle the rpms, and obviously it would overheat after so long, but it might tolerate a short dyno run.


----------



## Trigger-Time (Nov 26, 2010)

I was 12 years old in 1972, dad was letting me pull our H Farmall tractor
at local pulls. At one of the pulls they dyno tested the tractors for HP
for each class. The dyno looked very old, it was nice looking just
the way it looked made you think of something made in the 40's or 50's.
Anyway the man running the dyno was old and moved slow. I ask him
if he would like some help. He grinned and said, son I sure would. So
I hooked up the dyno to the PTO on tractors most of the night.

The dyno was hooked up to a garden hose, dyno had a few valves
he would turn to put a load on the tractor's. When dyno test was
done for each tractor he would let the water out of dyno. That
water has hot hot hot, the old man said I can kill any tractor here
with this old dyno.

I never thought to ask what was going on in the dyno.
I guess where to many young girls my age running around at the time. 

So was their a brake set up inside the dyno and the water
was just to keep brake cool?

TT


----------



## timberwolf (Nov 26, 2010)

I thought about friction brake dynos and even to handle say a 10hp ported saw the heat produce would be about equal to a conventional kitchen stove with all the burners on max. Just seemed like it was going to be too difficult to keep the runs short enough and RPM stable enough to get good data. Way too much of a PITA to do RPM points one at a time and if using a computer then it is at least as complicated as an inertia dyno plus need to deal with the load arm and load cell.

I think it would be pushing RPM limit for a standard disk break, even using big saw chain sprockets the mass wheel can get going 5,000 RPM.

But the brake dyno would be more usefull than inertia for tuning a carb or pipe at fixed RPM.

I'm going to look over the data capture again tonight, should be getting an RPM update every 0.025 seconds but the way the data is exporting I get one every .1 seconds and groups of 4 or 5 in a row read the same value, plus there is some ossilation, one group is a little high then the next a little low and the ploted power curve ends up rough. Messing around filtering the data I can smooth it out, but have not tested that to see if the end result is repeatable. 

Might try switching from optical to magnetic pickup and see if there is any difference.

I'd bet that tractor dyno was a waterbreak, kind of like two propellers pushing against each other to create a load.


----------



## madhatte (Nov 26, 2010)

Trigger-Time said:


> So was their a brake set up inside the dyno and the water was just to keep brake cool?





Called a water brake. What it is is a pair (or more) of counter-rotating fans inside a chamber with water pumped through. The water is both the fluid coupling medium (as in a torque converter) and the coolant. The two fans generate counteracting thrusts. The water has to be pumped in there at sufficient pressure to prevent cavitation or else the fans can free-wheel until the bubble collapses, which isn't good for any of the parts involved. I've seen some pretty big ones used as dummy loads for turbines. They seem to be pretty high-maintenance items.


----------



## mtngun (Nov 26, 2010)

Trigger-Time said:


> So was their a brake set up inside the dyno and the water was just to keep brake cool?


Most of the tractor dynos I've seen drove a big assed fan, but water pump dynos are common, too. Basically it's just a water pump, and you control the load with a valve on the pump output. Presumably he had some kind of load cell or spring scale to measure the torque applied to the pump. If you know the torque, and know the rpm, you can calculate the power.

One of the dynos that TW linked to used a water brake, prolly a scaled down version of your tractor dyno.

Pumps are expensive, though, and not necessarily designed to hold together at chainsaw RPMs. That's why I was thinking to use a disc brake, which can be had for not a lot of money. Yes, it would have to dissipate a tremendous amount of heat energy, but disc brakes do that all the time, and it wouldn't take that long to run a chainsaw through its paces. One of these days I oughta get off my butt and try it.


----------



## timberwolf (Nov 26, 2010)

To do it with a disk break it would likely be best to run 2 sets of gears with something like a 12:1 to 15:1 reduction to get the RPM down under 1000 RPM on the disk break then could use a steering knuckel and caliper set up off a FWD car, a little work to a master break cylinder and that could be the bigger part of the mechanical systems. Just mount the saw on a swing arm and load cell.


----------



## mtngun (Nov 26, 2010)

Ya, I dunno how many rpm's a disc brake could handle, so gear reduction would be desirable. I was thinking a motorcycle brake, maybe even a bicycle brake. Only way to know is try it -- from a safe distance. :hmm3grin2orange:

Entry level usb oscilloscope/data logger boxes  start around $50. I've never used one of the cheapo units, but the specs make it look do-able.

If only I had time ........ may have to wait for retirement. As you once said, it helps if you don't sleep.


----------



## Trigger-Time (Nov 26, 2010)

mtngun said:


> Ya, I dunno how many rpm's a disc brake could handle, so gear reduction would be desirable. I was thinking a motorcycle brake, maybe even a bicycle brake. Only way to know is try it -- from a safe distance. :hmm3grin2orange:
> 
> Entry level usb oscilloscope/data logger boxes  start around $50. I've never used one of the cheapo units, but the specs make it look do-able.
> 
> If only I had time ........ may have to wait for retirement. As you once said, it helps if you don't sleep.



If my math is correct.

30" dia tire at 70mph turn's 784rpm's

20" dia = 1176rmp's


TT


----------



## timberwolf (Nov 26, 2010)

Yep, I had about the same math, figured they should easy be good for 100mph and took a 30" tire and got just over 1000 rpm.

Would be more than a bicycle brake could handle, motorcycle maybe, but I would think it would be better to have something more substantial just for heat disipation. 

You don't want to brake or accelerate too fast with the break dyno or you measurments become affected as the whole thing starts to work like an inertia dyno. Also would have to take gear and friction losses into the driveline in. For a friction dyno that would need to be estimated. On the inertia dyno you can do a coastdown and measure how quickly the wheel slows, get a negative HP or torque figure for that then add it to the accelerations to take friction and windage losses out of the system.


----------



## Woodman 460 (Nov 26, 2010)

Great post T.W. I am happy to see that you are displaying such usefull knowledge here for us all. I hope to carryout some port work on my 361 this winter!


----------



## parrisw (Nov 26, 2010)

timberwolf said:


> I thought about friction brake dynos and even to handle say a 10hp ported saw the heat produce would be about equal to a conventional kitchen stove with all the burners on max. Just seemed like it was going to be too difficult to keep the runs short enough and RPM stable enough to get good data. Way too much of a PITA to do RPM points one at a time and if using a computer then it is at least as complicated as an inertia dyno plus need to deal with the load arm and load cell.
> 
> I think it would be pushing RPM limit for a standard disk break, even using big saw chain sprockets the mass wheel can get going 5,000 RPM.
> 
> ...



Hey, What kind of pickup are you using? You said optical, when I first saw the pics of your dyno it reminded me of the governors I used for my RC Heli's, you could use an optical or mag pickup for them, the optical pickup was very easily messed up with indoor lighting, had to be out in sunlight to work properly, and even then I had a hard time with it. I went to a magnetic pickup and all was good.


----------



## timberwolf (Nov 26, 2010)

I wasted the evening trying different pickup sensors, different numbers of triggers, about every setting I could and it just looks like the data logger is a POS as far as what I am trying to do. 

Sent an email to see what it is going to set me back to get the right electronics... GRRRRRRR!


----------



## timberwolf (Nov 29, 2010)

Here are a few carb pics, 044 and 361 carbs. both were taken out about 1.5mm in the venturi increasing the venturi area by about 20%. 044 and 361 carbs share the same 20.5mm throttle plate diamiter, but 361 is a lot tighter than 044 in venturi at 15mm vs 17mm and choke 18.8mm vs 22mm.

There is very little room to take out 044 carb as there is a fuel passage on the left hand side that runs very close to the bore. I ended up sleaving the passage with a brass tube to gain more space.


----------



## Tzed250 (Nov 29, 2010)

Thank you for the pics and info!!!


.


----------



## mtngun (Nov 29, 2010)

How do you know how much metal can be removed from the carb before running into trouble ? Is that a trial and error thing ? 

I'm thinking I best have a spare carb on hand before I attempt this. 

Thank you for sharing your knowledge, TW, you are too generous.


----------



## timberwolf (Nov 29, 2010)

It can be some trial and error, but looking the carbs over closely it is not too hard to pick out where the internal passages are and avoid the errors as much as possible.


----------



## parrisw (Nov 29, 2010)

timberwolf said:


> Here are a few carb pics, 044 and 361 carbs. both were taken out about 1.5mm in the venturi increasing the venturi area by about 20%. 044 and 361 carbs share the same 20.5mm throttle plate diamiter, but 361 is a lot tighter than 044 in venturi at 15mm vs 17mm and choke 18.8mm vs 22mm.
> 
> There is very little room to take out 044 carb as there is a fuel passage on the left hand side that runs very close to the bore. I ended up sleaving the passage with a brass tube to gain more space.



Awesome stuff!!! I like the carb holder! I see you always have 3jaw chucks in your pics, do you ever use a 4Jaw?


----------



## timberwolf (Nov 29, 2010)

I do use 4 jaw chuck for turning offset parts and square stock, that about the only time it gets used.


----------



## parrisw (Nov 29, 2010)

timberwolf said:


> I do use 4 jaw chuck for turning offset parts and square stock, that about the only time it gets used.



Cool, I try to use my 3Jaw most of the time, it just doesn't hold parts as good as I like, maybe a new one is in order, I find if I tighten it loosely then indicate it and tap the stock to get the best runout I can, it seems to work ok.


----------



## parrisw (Nov 29, 2010)

Anything special for boring? Or just a regular ol boring bar?


----------



## timberwolf (Nov 29, 2010)

Yep, used a boring bar, but sometimes have ground a small 1/4 HSS tool with a profile to do the edges of the venturi when removing choke plate and reworking the entry for a race carb.


----------



## Terry Syd (Nov 29, 2010)

The guys at the local shop took their carb for x-rays. They had several shots done at different angles so they could see exactly where all the passages were and how much meat they had to play with.

I wouldn't call what they ended up with as a 'carburetor', it was more like a pipe.

Brian, looking at the extensive work did to open up those transfer tunnels, is that a stock jug or the BB?


----------



## parrisw (Nov 29, 2010)

timberwolf said:


> Yep, used a boring bar, but sometimes have ground a small 1/4 HSS tool with a profile to do the edges of the venturi when removing choke plate and reworking the entry for a race carb.



Cool thanks! 

Say on a 372 carb? How much can you safely take out the venturi?

What are you indicating in the last pic? Is there really any room for adjustment?


----------



## timberwolf (Nov 30, 2010)

I would have to look at a 372 carb, been a couple years since I worked one of those over, the are a few different carbs found on the 372.

Last pic was just checking centering of the carb.


----------



## SpaayDawg (Nov 30, 2010)

Just subscribing to this thread. Great read and material content. Please keep it coming!!


----------



## Grande Dog (Nov 30, 2010)

Howdy,
Back in the day when we were messing with velocity stacks, we used t-handled tapered reamer to adjust the venturi. It can be done without a machine tool.
Regards
Gregg


----------



## AUSSIE1 (Nov 30, 2010)

I had a pin hole through to a passage that wasn't visible to the eye and the only way to find it was by pressurizing the carb under water. A dab of the wife's nail polish sealed it up and doesn't break down with the fuel.


----------



## timberwolf (Nov 30, 2010)

> we used t-handled tapered reamer to adjust the venturi.



Yep, others pretty much must be done with a hand grinder due to odd shaped venturries or bulges over passages.

If you want to work over the diamiters under the throttle or choke plates though that needs a little mor precision.


----------



## Tzed250 (Nov 30, 2010)

timberwolf said:


> Yep, others pretty much must be done with a hand grinder due to odd shaped venturries or *bulges over passages*.
> 
> If you want to work over the diamiters under the throttle or choke plates though that needs a little mor precision.



Do you mean like the WJ-69A has in it?


----------



## Zombiechopper (Nov 30, 2010)

Brian, would you see any benefit in putting an 044 carb on the 361? I'm a little leary about grinding a carb, was just wondering if the larger carb would work well (aside from the expense of buying a carb). Or is it necessary to run the smaller carb for idle stability etc?


----------



## timberwolf (Nov 30, 2010)

I was planning to try this, but there are some problems to overcome, it would be far from bolt on. The choke shaft is not indexed correctly to mesh with the 361 linkage, pulse line is fed through face of carb on 361 and direct to carb on 440, fuel curve may need some tweaking and a couple other issues. But I can't see any reason I can't make it work.


----------



## Terry Syd (Nov 30, 2010)

I figured out from the bit of gasket material on the ported jug that it was the stock jug. That is a fair bit of work on the transfer ducts to get it to flow, I'm waiting to see what you do with the BB!

What is the material you used to measure the cross section of the ducts? It looks like some sort of material that will set and then can be extracted and measured. The guys in the Dolkita BB thread would probably find that stuff useful.


----------



## timberwolf (Nov 30, 2010)

Just modeling clay. Works well for measuring and casting external transfers too.

Just moved flow bench to the basement, so will get some flow info going.


----------



## Terry Syd (Nov 30, 2010)

Do you make a couple of runs, one without the piston in place and another with the piston set at BDC? I've always wondered how much, if any, restriction is caused by the flow around and through the piston.


----------



## timberwolf (Nov 30, 2010)

Actually I have a positioner built into the bench so I can move the piston up and down and load flow info into computer as piston moves. It is quite a bit of work to set up though. So, for looking at port flow I am finding it more practical just to position the piston by hand and measure flow.


----------



## timberwolf (Nov 30, 2010)

Flow tested a few carbs.

26.7 cfm @ 20 inWC - 361 stock
29.3 cfm @ 20 in WC - 361 moddified
30.4 cfm @ 20 in WC - 440 stock
32.4 cfm @ 20 in WC - 440 moddified

There is a bit of +/- on the numbers as the calibrated orifice was 1.500 and would get better resolution with a smaller orifice.


----------



## mtngun (Nov 30, 2010)

Thanks for the excellent flow data, TW.

Any drawbacks to modded carbs, assuming it is done well ?


----------



## timberwolf (Nov 30, 2010)

If it is done right and fuel curve tweaked back to shape there should be little drawback. 

However at part throttle lower speeds (say 5-7k) there could be more difficulty with break up of fuel due to lower velocity.

New 361 air filter flows very well, ~63.9 cfm @ 10 inWC

Which actually outflows a new HD filter off the 440.

47.9 cfm @ 10 inWC with dust band on
56.4 cfm @ 10 inWC with dust band off


----------



## 2000ssm6 (Nov 30, 2010)

I got a Maxflow kit I give ya for testing purposes if you think it is worth doing. Came off a 460, I know they work but they are dang ugly.


----------



## timberwolf (Nov 30, 2010)

I might have one of the max flow filters about, not sure. They are ugly and likely not much need. One day when I get the dyno dialed in with some better electronics it would be a good test to see if any difference could be picked up between filters.


Just for the heck of it flow tested the mufflers though it really won't tell much accuratly about non steady state flow under running conditions.

12.1 cfm @ 20 in 361 stock muffler (screen made no measurable difference) 
46.7 cfm @ 20 in 361 single port 21.1mm
50.0 cfm @ 20 in 361 dual port 20.5mm


----------



## Trigger-Time (Nov 30, 2010)

timberwolf said:


> I might have one of the max flow filters about, not sure. They are ugly and likely not much need. One day when I get the dyno dialed in with some better electronics it would be a good test to see if any difference could be picked up between filters.
> 
> 
> Just for the heck of it flow tested the mufflers though it really won't tell much accuratly about non steady state flow under running conditions.
> ...



Have you ever tested 361 muffler after singel port.
Then removed muffler guts and re-tested?

Or stock muffler before and after guts removed, no MM


TT


----------



## parrisw (Dec 1, 2010)

timberwolf said:


> I would have to look at a 372 carb, been a couple years since I worked one of those over, the are a few different carbs found on the 372.
> 
> Last pic was just checking centering of the carb.



Sweet thanks. Maybe one day when I feel brave, I'll bore one out.

When you do your tube style muffler mods, do you feel it makes any difference if you extend the tube inside farther? I usually just keep em short.


----------



## Terry Syd (Dec 1, 2010)

Brian, I looked at your flow figures for the mufflers and something came to me. I made up a muffler mod that is relatively quiet that utilises the tubes for the mounting screws.

Some guys have taken a grinder through the exhaust port and cut a hole in the tube to use them for exhaust tubes. Unfortunately, since the opening is in direct line with the exhaust port the sonic wave goes straight out the tube and makes the muffler louder.

I chose to drill a small hole in the side of the muffler that I could stick a Dremel tool through and cut a hole on the side of the tube opposite of the exhaust port. The sonic wave can't exit directly out the hole. If the hole on the side of the muffler is kept small enough to just allow the Dremel bit through, the simple patch on the outside is virtually unnoticeable - a stealth muffler mod.

If you ever get some time to play with the stock muffler, it would be informative to see how much that mod increases the flow.


----------



## timberwolf (Dec 1, 2010)

I'll do some more on the stock mufflers some time. There are hundreds of ways to go at them, could be a study all on its own to produce maximum flow with minimum sound levels. I think it is quite likely the baskets in these mufflers help cut some of the sound levels too as the look very much like the insides of a silencer on an exhaust system.

On tube flow I messed with on the flow bench I found up to a point, longer tubes produce more flow per area which would be related to coefficient of discharge. Also, I think they act as a bit of a backflow preventer of sorts blocking some outside air from getting into the muffler and diluting chage at low RPM. The result is needing less LS fuel enrichment to get the same high RPM flow capacity.


----------



## mtngun (Dec 1, 2010)

timberwolf said:


> 12.1 cfm @ 20 in 361 stock muffler (screen made no measurable difference)
> 46.7 cfm @ 20 in 361 single port 21.1mm
> 50.0 cfm @ 20 in 361 dual port 20.5mm


Great data, TW. :yourock:

That's good to know that the screen made no difference. I would never have guessed.

Your data illustrates rapidly diminishing returns beyond a modded single port, just as we have been saying all along. 

I can't say enough good about you and the other experimenters who unselfishly share results and particularly the measurements.

You gonna write a book on all this stuff someday, TW ? 'Cuz I would buy it.


----------



## timberwolf (Dec 1, 2010)

I try...

The screen makes no difference as it's area is huge compared to the bottleneck between the screen and the outlet.

I think the dimminishing returns in the case of these two mufflers is the matter of the restriction entering the muffler showing up. Next 361 I have open I will test the flow entering the muffler. When the outlet area is greater than the inlet it makes sense that addition outlet would not give more flow. Some of the difference may have been the difference in the inlets as they were matched to the flanges and the DP muffler was opened just a little more on the inlet side too.

When the muffle is bolted to the cylinder things would change and the coefficient of discharge into the muffler would jump from somewhere just over 0.6 to closer to 0.8 due to improving the shape of the orifice/nozel changing it from a simple hole in the back of the muffler as it was tested to a not to bad nozel formed by a radius edge port and tapered exhaust flange.


----------



## madhatte (Dec 1, 2010)

Great stuff. I'd rep this whole thread if I could. Solid, reproducible empirical data always makes me happy!


----------



## Trigger-Time (Dec 1, 2010)

mtngun said:


> Great data, TW. :yourock:
> 
> *That's good to know that the screen made no difference. I would never have guessed.*Your data illustrates rapidly diminishing returns beyond a modded single port, just as we have been saying all along.
> 
> ...



Am with you 110% on TW 


About, Stihl's muffler screen, it's so much bigger than the exhaust port
that more flow can get threw screen than the port. I didn't think of that
on my own. Think I have read it in post by TW and Lakeside.


TT


----------



## Tohya (Dec 1, 2010)

Great work timberwolf!

As long the screen isn't mounted directly to the outlet hole, and at least twice the area, it shouldn't cause a restriction.

The deflectors with the screen between them and the muffler would cause a restriction. But you can just use a larger hole with the screen to make up for it.


As a side question, are you using the MOTA 2 stroke engine simulator? What do you think of it and have you tried any other software?

I was looking around and ran across the trial version of Lotus Engine Simulation, which is restricted to just one cylinder in the trial. It will simulate a 2 stroke so I'm going to try it out.


----------



## timberwolf (Dec 1, 2010)

I am using Mota, some of Blairs older dos stuff and have a few other programs for doing pipes and specific calcs, also have put quite a number of my own calcs into spreadsheets to do things like squish velocity, compression estimations, time area, pipes, flows and such.

I like Mota and have been using it for a few years, it does some things well, others not so well and some not at all. It is a steep and somewhat frustrating learning curve just to get using the software and it takes a lot of time to measure and enter engine data when starting out with a new motor. It is really going to be best for someone who already has a strong understanding of motors and has read some books on 2 strokes, otherwise it could be quite confusing to tackel as it is very much a garbage in garbage out type software.

It is not smooth running software like you get with windows, it is more typical if engineering software, if you don't enter data correctly it won't always tell you, it just quits and the computer needs to be rebooted before it will run a new simulation. 

Mota does not do a great job of exportable files for graphs, jpegs ect.
It does not do well at designing a pipe for you but is pretty fair at testing a design you come up with.

It does make good comaprisons of different changes to engine designs, but does not give accurate HP readings without a lot of calibrating it agains known engines. No parametric analysis, each change to a variable requires a whole seperate data file and simulation run.

After I used it quite alot for a year I was still finding usefull features. 

To sum it up it is good at testing designs you come up with, but will not help much with teaching how to come up with the design for a good port job.


----------



## Terry Syd (Dec 1, 2010)

"On this one I kept the transfers almost stock height by the time the jug gets lowered. And went back about 1mm on the front and 3mm on the rear."

I assume that the increase in the width of the transfers was not simply a flairing of the angle of exit, but an actual increase in the time/area of the ports (and thus the necessary extensive work on the transfer ducts).

You've mentioned before that you have had good results using a transfer time/area slightly below Jenning's figures, I'd really like to know what figure you are working with (I won't tell anyone).


----------



## timberwolf (Dec 1, 2010)

Range I like for transfers on 361type motor is 0.000073 to 0.000093 But it moves around some depending on bore to stroke ratio. I'm right at the top of the range if not a little over on this one.

Another thing I will look at is port velocity. Here are a couple charts @12,000 rpm, the purple line is the one to look at one is the front pair of transfers the other the rear. In general I don't want to exceed 1/3 the speed of sound in transfers or intake otherwise the air starts to compress and decompress more than flow as it should.

Also in the charts it is easy to see there is very little reverse flow in the transfers when they open, a good indication of sufficient blowdown.


----------



## Terry Syd (Dec 1, 2010)

Good stuff, I've got my transfers at the bottom of your range for 10,000 RPM. I don't think I can go any higher unless I can get some more CC compression.

Looking at the two charts, I can see that the front transfer port is reverse flowing prior to closing. I would have thought that the reverse flowing would have occurred at below peak torque. Do you think that there may have been a positive wave coming in from the exhaust to affect the flow at that port without affecting the rear port?

If so, that opens a whole other can of worms for muffler design.


----------



## timberwolf (Dec 1, 2010)

Quite possible it is, would have to look at some of the other pressure and wave graphs and see where that pressure is coming from.


----------



## Terry Syd (Dec 1, 2010)

Yeah, wouldn't that be a hoot to find out that a positive pressure wave was bouncing back from the front of the muffler - so we put a spacer under the muffler to get the wave to return after the transfers close and we 'pack' the combustion chamber a bit tighter. It ain't a pipe, but I will take what I can get.


----------



## parrisw (Dec 1, 2010)

Terry Syd said:


> Yeah, wouldn't that be a hoot to find out that a positive pressure wave was bouncing back from the front of the muffler - so we put a spacer under the muffler to get the wave to return after the transfers close and we 'pack' the combustion chamber a bit tighter. It ain't a pipe, but I will take what I can get.



There is a tool available, in the auto industry, its a very sensitive pressure sensor used to measure exhaust pulses, you can actually see a leaking exhaust valve with it, by seeing the negative pulse as the engine sucks exhaust back into the engine. Its possible that it could be used to measure the exhaust pulse's/pressure wave's in a saw exhaust? Thought's?


----------



## timberwolf (Dec 1, 2010)

> Yeah, wouldn't that be a hoot to find out that a positive pressure wave was bouncing back from the front of the muffler - so we put a spacer under the muffler to get the wave to return after the transfers close and we 'pack' the combustion chamber a bit tighter. It ain't a pipe, but I will take what I can get.



On race engines I have played with that idea and there is something to be gained, far from worth it on a work saw though, also the width of the poweband seems to be very narrow, likely because it is working off a harmonic of a full cycle which would makes sense as the muffler is far shorter than a tuned pipe.


----------



## Trigger-Time (Dec 2, 2010)

timberwolf said:


> If it is done right and fuel curve tweaked back to shape there should be little drawback.
> 
> However at part throttle lower speeds (say 5-7k) there could be more difficulty with break up of fuel due to lower velocity.
> 
> ...



This is the one that really fooled me, so 361 filter will flow more than MS660
and MS880 air filter then also. AS 440,460,660 and 880 all use same filter.



TT


----------



## timberwolf (Dec 2, 2010)

Yep, I had to double check it, tested 2 new filters from each and yep the 361 air filter flows more than the HD used on Stihl 440 through 880. 

I kind of remember flowing the HD at what I thought was closer to 100 cfm but might have been off base with calcs as it was right back when I was just getting the flow bench working.


----------



## Trigger-Time (Dec 2, 2010)

timberwolf said:


> Yep, I had to double check it, tested 2 new filters from each and yep the 361 air filter flows more than the HD used on Stihl 440 through 880.
> 
> I kind of remember flowing the HD at what I thought was closer to 100 cfm but might have been off base with calcs as it was right back when I was just getting the flow bench working.



I have kicked around the idea of cutting center out of HD filter.
Then glue two HD together. Install longer stud for filter in my 066 milling saw
and run 2 HD filters. With alum. plate and nut to hold them on saw.



TT


----------



## timberwolf (Dec 2, 2010)

Slick idea! 

Likely would not even need to glue them they should seal on them selves.

If you could put a screen over the whole works to help shead the larger stuff it would help too. Filtration for milling is one area where I like the husky design over the stihls as the stihls plug up fast.


----------



## Trigger-Time (Dec 2, 2010)

timberwolf said:


> Slick idea!
> 
> Likely would not even need to glue them they should seal on them selves.
> 
> If you could put a screen over the whole works to help shead the larger stuff it would help too. Filtration for milling is one area where I like the husky design over the stihls as the stihls plug up fast.



For screen, was thinking about pantie hose.

What I would really like to do is make a PVC intake pipe about
16" tall. Then I could make it take a small engine or automotive filter.
But then would have to brace it up for support. But the 2 filter deal
will be enough I think.


TT


----------



## blsnelling (Dec 2, 2010)

timberwolf said:


> If you could put a screen over the whole works to help shead the larger stuff it would help too. Filtration for milling is one area where I like the husky design over the stihls as the stihls plug up fast.



Outerwears are awesome for that.


----------



## timberwolf (Dec 5, 2010)

Finnished the mufflers up.


----------



## parrisw (Dec 5, 2010)

timberwolf said:


> Finnished the mufflers up.



I love the muffler hanger!!


----------



## timberwolf (Dec 5, 2010)

Some work on the next 361.

Plugged the hole in the bottom of the intake, always wondered what this hole was for, best I could figgure it was a drain to keep fuel from making a puddle in the boot causing a stumble on acceleration.

Roughed in the upper transfers, a little wider than the other saw, but kept them low, Still need to clean the corners of the front transfer a bit.


----------



## timberwolf (Dec 6, 2010)

Here is some rough in work on the moddified intake flange.

Can just make out where the old passage was before being pluged with a 3/32 aluminium filler rod.


----------



## mtngun (Dec 6, 2010)

Nice work, TW.


----------



## timberwolf (Dec 6, 2010)

Couple pics from the inside of the intake, not a lot of piston skirt width to work with but can grab about 1mm on each side and have extended the durration a little but gained a fair bit of area by re-shaping. Also because the carb and rest of intake will be able to flow a good bit more than stock the base can be filled quickly so alot of intake duration is not needed.


----------



## Outlaw5.0 (Dec 6, 2010)

What did you use to fill the hole?.


----------



## timberwolf (Dec 6, 2010)

3/32 aluminium filler rod with a skim of JB.


----------



## Terry Syd (Dec 6, 2010)

Looks like you may have slightly enlarged and smoothed some of the areas in the piston. I've always wondered about how much the piston affects the flow. Have you been able to detect a difference in flow by reworking the piston a bit?


----------



## timberwolf (Dec 6, 2010)

Yes, took off some of the rough edges on the piston. Would be a really good experiment to flow the whole saw case and transfers to see how much flow could be improved with piston work alone.


----------



## mtngun (Dec 6, 2010)

Impressive amount of sweep back on those upper transfers.


----------



## Thorcw (Dec 6, 2010)

Hey I know I asked on the 440-460 build but how do you do the ceramic coating (im guessing like powdercoating) and were do you get the stuff at?


----------



## Terry Syd (Dec 6, 2010)

From the earlier picture where Brian roughed in the rear transfer port -

http://www.arboristsite.com/attachment.php?attachmentid=160800&d=1291590345

It looks like he has now worked that swep backed area (changed the angle of discharge) to make the port wider in order to pick up more area of flow. The jug is starting to look more like a motorcycle cylinder with those wide transfer ports.


----------



## timberwolf (Dec 7, 2010)

> The jug is starting to look more like a motorcycle cylinder with those wide transfer ports.



Yes, looking to get a little more RPM with this 361, maybe not quite as much torque. Wait till I get to the BB, have a couple ideas for that one that I have not tried before.

The ceramic sprays on as a wet emuslsion and is baked which I think activates some polymer binders to hold the ceramic dust together. Coating is not as good as with pistons I have sent out to be coated (some fuels will eat at it), but a fraction of the price.


----------



## timberwolf (Dec 7, 2010)

Exhaust side

Port is offset to one side more due to the lower ring end pin location.


----------



## Trigger-Time (Dec 7, 2010)

timberwolf said:


> Exhaust side
> 
> Port is offset to one side more due to the lower ring end pin location.



Outside of cylinder, looks as if exhaust port center is in line with casting marks
on outside of cylinder, if it is.
Does the port angle from inside to outside of cylinder?

Or does exhaust blow out left to right or other way around?

Port walls look very, very smooth!

It sounds right in my head, if you know what I mean.


TT


----------



## Terry Syd (Dec 7, 2010)

Nice looking port, too bad about the ring end. Do you think it will have an effect on symetry of flow? 

I suppose after you have run it a bit you can check the carbon patterns and then make a decision about keeping the lower ring.

Looking back on your original computer simulations I noticed that the curves were essentially the same except that they gained in amplitude. Are those curves still valid with your decision to increase the transfer area on this new jug? If not, if you get a chance to run another simulation with the increased transfer area, I'd like to see how it affects the curve.


----------



## timberwolf (Dec 7, 2010)

I have moved the second ring end before though there is almost nowhere to put it that it does not hit ports and I have run them without for racing, but as this is still a full on work saw...

The exhaust does head out a bit right to left looking at the back as the saw is held. I don't really think this makes any huge difference on scavenging, at least I have not noticed.

Here are the lower transfers, tool makers ink which I was using to mark height all over everything.


----------



## timberwolf (Dec 7, 2010)

Cylinder base turned down 0.018 and piston poped up 0.025 with 40 deg shoulder.

Cleaned up casting flash on piston as well.


----------



## Terry Syd (Dec 7, 2010)

Wow, that is pretty. You removed some of the cylinder at the transfers, was that to assist in porting or to unshroud the piston (or both).

Nice work on the piston to get it to flow. You might even want to trim some of the extra metal off the outside of the wristpin hole, I doubt that the circlip needs that much metal to hold it in.

That looks fast just sitting there!


----------



## timberwolf (Dec 9, 2010)

It's not quite right yet, RPM is a little lower than it should be and compression a little lower than is should be. 

Running not bad though about .1 seconds faster than the other 361, but it should be a little quicker.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/Q-BJzCiJBdM?hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/Q-BJzCiJBdM?hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

Was really pushing on the second cut.

A few pics, muffler inlet before opening it up to match the flange, piston and cly.


----------



## Terry Syd (Dec 9, 2010)

What about bumping up the crankcase compression a tad to push the powerband higher?


----------



## timberwolf (Dec 10, 2010)

I think there is something else going on. I did find 10 pounds of compression, the decomp button was leaking a little. 

A couple of changes in mind. 

1 redrill a smaller and slightly relocated passage in the intake. there is a slight fuel pooling problem and tilting the saw front to back after ideling can make it stall.

2 increase exhaust durration about 4 degrees.

3 increase compression about 5-10 psi as raising the exhaust a little further will lower it some.


----------



## mtngun (Dec 10, 2010)

timberwolf said:


> redrill a smaller and slightly relocated passage in the intake. there is a slight fuel pooling problem and tilting the saw front to back after ideling can make it stall.


Thanks for experimenting with that little hole, TW. Now we know what it is for.


----------



## ronT2 (Dec 11, 2010)

Great thread timberwolf!

What kind of rpms is it turning in and out of the cut?

I like how you lengthened the upper rear transfers. I’ve tried it on a couple of my saws but not to that degree, I always worry about losing port velocity.


----------



## timberwolf (Dec 12, 2010)

Only 14,200 or a little more out of the cut, I would have expected closed to 15,000.

For keeping it as a good usable worksaw this is a better approach to the intake than plugging the vent, rock stable idle no matter how much shaking or tilting. Just roughed it, still a little finnishing to do.


----------



## Zombiechopper (Dec 12, 2010)

that's weird. I've got 15000+ with tons of four stroke on mine and not near as much tweaking done to it. Mine is max width ports, upper transfers similar to yours and lower transfer windows opened a bit. I've got mine at .018 squish without a popup. all stock timing. Is something with the timing hurting your RPM? 
Just wondering why the revs are topping out on that saw


----------



## timberwolf (Dec 12, 2010)

Yeh, it is strange, I'm going to swap another stock carb on and check that, maybe swap on another coil just to be sure. Power is there, just unloaded RPM seems a bit low and I would like to know why as the porting should be letting it rev up more.


----------



## Terry Syd (Dec 12, 2010)

That transfer work took a lot of meat out of the crankcase and increased the volume. I'm still wondering if an increase in the crankcase compression might be warranted.

With the increased transfer area you provided, I don't think you have to worry about narrowing the powerband with some more CC compression, the existing powerband would likely just shift up higher in the RPMs.

Stuffing the crank pin is easy enough, and if you can get a couple of sealed bearings for the crank, it might be worth the experiment. You could always pull one or both bearings out later.


----------



## timberwolf (Dec 13, 2010)

I tried it with a cylinder with much less removed on the transfers, about same RPM which is making me suspect either coil or carb.

There is not alot of volume inside the pin to stuff, 1mm tapered pin. Also I would worry about lack of cooling from the inside of the pin, These pins get enough heat to turn them interesting collors as it is.


----------



## timberwolf (Dec 13, 2010)

A little tweaking on carb and a little cutting time and it has picked up some.

RPM still in the mid 14K range but it is cutting smooth and strong so not going to complain.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/Pnda3-G0TJ0?hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/Pnda3-G0TJ0?hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


----------



## Trigger-Time (Dec 13, 2010)

That makes me smile 

What wood is that?.......and has it been cold enough up there for the wood to be frozen?





TT


----------

