Porting tools

[rmihalek]

Anyone care to discuss/reveal their favorite tools for opening up the ports on small bore chainsaw cylinders? I've got a 44mm bore to reach into to work on some transfer ports and I'm at my limit with my tools.

Also, what's a good way to measure these tiny ports? I can't fit my calipers in there!

 

[ehp]

get yourself a degree wheel, take your clutch drum off , i use a piece of plastic pipe that will fit the crank end and the degree wheel fits over the pipe, take a piece of wire to make yourself a marker , wrap the wire around your bar studs and after you mount your degree wheel to the crank bend the wire over the degree wheel so you can tell how many degrees you are turning your motor, with the jug on the saw , with the muffler off and the sparkplug out of the jug, put a light into the sparkplug hole, now look through the ext. port with the piston on top start being it down towards the bottom, look to the side inside your jug and you will see your transfer ports start to open, get as close as you can to the top of your piston to the top of your transfer port , once you think you are right on ,set your degree wheel at zero, turn the motor over going down then back up to where the piston just closes the transfer port, take the number of degrees and divide it by 2, this is your degrees for your transfer port, that is the best way to measure a port

the tool I have is from Foredom , it is a 90 degree head on it and is 7/8 of an inch long and has bearings but not cheap, i have heard of some guys using a little grinding wheel to get at the ports but not for me

 

[Al Smith]

Porting ,my way

First of all,I am not a pro,but rather a shade tree mechanic,with a little knowledge .I use 2 Dremel tools,one with a right angle drive.I use carbide burrs,for the roughing cuts,then silicon boron type,tiny grinding wheels .For the finish,I use Krayton [ impregnated rubber] type .Final polishing is done with felt fobs,and 3 grades of jewlers rouge .A good light and a mirror are helpful ,as well as a lot of patiance.The picture,is a McCulloch,naturaly.This is not mine,but sent,just for an example.I don't go that radical.

 

[thf]

You can buy all of your porting Tools at C.C. Specialty I think you can find them on the net..........

 

[Mange]

Don't stop now, tell some more about this power porting we all read so much about.
For ex.
A saw that is not piston ported, can it be done so?
Open fluch ports????
The hight of piston?
Does it need other carbs?
Is there power to gain just by polich?
And the heat, does the lost of material make it more sensetive?
What about...........

Perhaps I can wait a little with the other questions.

Mange

 

[Al Smith]

More porting

Well Mange,you have to look on the ports of a 2 cycle engine,in the same way you would the valves in a 4 cycle.In a 4 cycle,you change the valve timing,by altering the cam shaft.In a 2 cycle,you change the "valve timing" [for want of a better word] ,by altering the opening and closing time of the ports,in relationship to the piston .The proceedure,falls under a broad catagory of loop scavanging.I might add,at this point,that I personally know very little about the complexities of this proceedure.The type porting I do,is simpley to increase,or improve flow movement of the fuel mixture and resultant exhaust gasses.It would,most likely,be more properly term,polishing .The last one I did,was on one of my Mac 125s,and I doubt if I increased the actual horse power any more than 1/2 HP,but it does run very well .If you do a search of this site,there are other,older threads,covering this subject ,also,a good web site,is "Macdizzys" [I hope i spelled it right]

 

[Ax-man]

I hope this isn't too dumb of a question(s).

I've been over to McDizzy"s site and printed about every thing there is on the subject.

My question is on the degree wheel. Can a degree wheel be purchased some where for saws, because Mc Dissy's site is more geared to to motorcycle engines and snowmobiles.

If I wasn't sucessful in locating a degree wheel, could one be fabricated using the flywheel from the saw as a template for the size of the circle and mark it off with a protractor, and then fastening it to the crank of the saw in the same way ehp was describing.

Another dumb question.

If you were to widen and enlarge the area around the port, but do not disturb the size or shape of the port where it comes in contact with the piston,( not changing the timing ), would this up a saws performance or would it be the same. I'm going to get brave one these days this winter and give this porting a shot, on some saws I've been accumulating, just to see if I can do it and hopefully will still run right.

Thanks

Larry

 

[Crofter]

Do a google search for "degree wheel" you will find several that show printable copy. Download and glue to a stiffer backing for a workable degree wheel.

If you have the patience to chase them down there are threads here about the pros and cons of doing your own porting.

 

[Ax-man]

Thanks Frank, I didn't think it would be quite that easy .

I've been through alot of the threads here and have some printed, when I get closer to doing this I'll be doing more searching to see if I missed anything.

Thanks again

Larry

 

[Al Smith]

More on the subject

I have enclosed a picture of a stock ported McCulloch 91 kart engine.If you compare it to the picture of the ported one,In my previuos post,you will see a vast difference.For example,the whole area,in the ported version,has been polished,and relieved,in addition to being raised,and widdened.If your question refered to basicaly just improving the flow pattern,by relieving the port area,in regards to changing the port timing,no,you would not change the timing.I would suggest,however,that you practice on a saw that is not your best,or a "garage sale"special cheapie.I am fortunate to be able to refer to my good friends porting charts,as he was one of the national karting champions ,in the USA,during the 70's.He,like most engine builders,will not give away all their secrets ,but then I wouldn't myself .Give it a try,maybe you will get some secrets of your own

 

[Toddppm]

Al , could you post a larger pic of the first ?

 

[spacemule]

Here is an blown-up version of the first picture, but it's not good quality.

 

[rmihalek]

Hey Al, what is that a picture of? Are those three holes the exhaust port?

 

[Al Smith]

Intake ports

That is the carb. side intake port of a reed valve McCulloch engine.These engines had a set of transfer ports,also,directly accross from the main ,on the other side of the cylinder.The pic.,shows the exhaust of a Mac125.