removing gasket to increase squish

[sclarke]

I have heard of people deleting the gasket for the cylinder to increase squish. It kinda makes me nervous, not using a gasket at all but I know smart people do this. so is there any possible way to damage the saw? could this allow for air to get into the crankcase? what do you think?

 

[clemsonfor]

Damage not checking the squish and having the piston slam into the head. You increase compression. But if u don't seal it with nail polish or brush on sealer so something u won't seal right. No expert but had it explained to me when I was going to think about it.

 

[clemsonfor]

Still debating about it if and when I pull the 372 apart to put in the set of Cabers I have.

 

[Fifelaker]

Don't use nail polish! Yamabond, Hondabond Or Dirko. I may have missed a few brands but use something designed for the application.

 

[clemsonfor]

What I was told. Have not done my research yet. What about rtv silicon?

 

[Fifelaker]

See above post.

 

[Rock Crusher]

RTV silicone will fail from the gasoline mixture. A good product would be Loctite gasket eliminator #515 used with their spray primer-good for 0.050" gap.

 

[sclarke]

thanks for the advice on gasket sealers. I generally use dirko with good results. my question had more to do with if it is possible to damage a crankcase or cylinder by eliminating a gasket in order to increase squish. anyone have any thoughts on this?

 

[clemsonfor]

Higher compression motors would be harder on bearings a they increase power but I don't think this mod would be enough that you would see any difference. In bearing wear that is. Also the starter handle will want to snap back more if u give it a sissy pull.

 

[kevin j]

It is not just 'remove it and hope' but it is not rocket science either. You can do it.

Factory parts have to go together will all the tolerance stackups in the wrong direction, so if tolerances go the other way, squish can be wide and lose compression. Basically you are sort of 'blueprinting' the exact combination of parts you have in hand regardless of the build tolerances.

You will need to measure existing squish with gasket in place before teardown, or before you put the new rings on. Do 4 or 6 places around the piston, with thin soft solder through the spark plug hole, to the very outer perimeter couple mm of the piston/cyly/head. Rotate engine carefully so it smashes the solder. Remove and measure solder thickness. Then measure gasket thickness and see how it would change. You can also make an intermediate thickness gasket from solft alum pop can, manila folder, typing paper, whatever you want for thickness. Or run without using the gasket if the numbers are ok. You can use dial or vernier calipers if you don't have micrometer. That is plenty accurate.

I use Permatex engine casing sealant, don't recall the number, but it is grey. Motoseal I think called. Many are fine. But not silicone.
Check Arborist site for the 372, but usually .020 to .025 is minimum clearance.

Bumping compression helps, sometimes a lot. Especially if you do some mild port cleanuup, maybe widen exhaust but not change the timing, and open the muffler.
I use 91 octane fuel in all small engines because it is no alcohol, but that is plenty of octane. Since the manuals usually say 87 or 89 I don't think you should have any fuel problems with detonation. Saws are small cylinders and high rpm and can tolerate a lot.
Check your compression before and after just for records sake, then run 5 or 10 tanks and check compression again. It will bump up as it seats in.

Doesn't overstress bearings unusually. Sure, the B10 life probably goes from 20 years to 15 years for a homeowner, but........

Change crank seals and fuel line, filter, pulse line. All cheap and do it all at once. Not risk an air leak taking new rings and piston.
The work is worth it if you are doing rings. New rings, very mild port cleanup, muffler mod. 372 is a hard worker and responds well. Lots of port info on AS from mild to wild.

kcj