Piston work on an 026

[Skooks]

I'm replacing the P&C on my 026 and am considering modding it a bit while I am at it. Any reason not to raise the intake-side piston skirt 1 mm? Does this have any negative side-effects?

 

[Four Paws]

Well, if you are going to trim the intake side of the piston skirt, you better raise the exhaust port the same ammount and open up your muffler (muffler mod). Imagine inhaling normally and exhaling through a drinking straw - kind of exagerating here, but you get the idea. More intake time area doesn't do much if you cant exhaust the burnt gasses. The 1mm number gets thrown around a lot: Many feel it is fairly 'safe' when performing a mod to a saw without actually doing the work that many feel necessary (like measuring the port timing, ie. degree the saw). If one cuts too much material, your durations and time area will increase beyond optimum and your saws performance will not improve, or decrease. Many don't like to trim the piston skirt as they feel it is a booty-fab approach to modifying the saw...that said, it is your saw; do your research and make your own decision. Pistons are cheaper than cylinders.

 

[Lakeside53]

Not sure I'd raise the exhaust port 1mm on an 026... I don't have the numbers, but it would dump the compression. I do however agree with paws - don't just raise the piston skirt unless you are going to do a lot more work.

A simple muffler mod will do far more than just raising the intake skirt.

 

[Skooks]

Mods

Thanks for the words of wisdom guys. I will stick with the muffler mod and maybe clean up the intake port just a bit.

Skooks

 

[timberwolf]

Lowering the bottom of the intake port gives you 125% of what the same change to the skirt will give you, and without the balance and strength issues associated with cutting the piston.

Beter idea yet to widen the intake before lowering it, keeps base compression up while increasing time area, moving peak torque up in RPM. But as posted above, not a lot to be gained changing only the intake without working the exhaust and other aspects.

 

[SmokinDodge]

Lowering the bottom of the intake port gives you 125% of what the same change to the skirt will give you, and without the balance and strength issues associated with cutting the piston.

Beter idea yet to widen the intake before lowering it, keeps base compression up while increasing time area, moving peak torque up in RPM. But as posted above, not a lot to be gained changing only the intake without working the exhaust and other aspects.

Interesting premise TW. How much wider would you recommend making the intake over stock? I realize it's a shotgun answer but the 1mm piston trim is as well and it seems to work well across the board.

 

[NWCS]

for the best performance allways leave the piston skirts alone. porting depends on how wide the skirt is, how long it is, stroke.. many things must be looked at when you are factoring what gets ported how much. if you look at the 026 videos on my website, that saw has a 100% stock untouched stihl piston. all that power was gained with a plain ol woods port and custom carb/intake. with a pipe it runs 19,000RPM in full race tune. i have not tached it with a muffler but she cranks out some RPM.