Can some please help explain the desired squish everyone is talking about.

[Grafton8]

I’m just in the middle of rebuilding a ms291.
I’m currently waiting on some cut clips to install the new piston.

what is the desired squish everyone is referring to.
This saw does not have a base gasket and I’ll be using motoseal as the gasket.

thanks

 

[cuinrearview]

You are not going to be able to change squish on that saw.

 

[frank_]

the squish area is important for combustion/burn if thats what you mean ?

 

[Mad Professor]

I’m just in the middle of rebuilding a ms291.
I’m currently waiting on some cut clips to install the new piston.

what is the desired squish everyone is referring to.
This saw does not have a base gasket and I’ll be using motoseal as the gasket.

thanks

It's the clearance between the piston and the cylinder combustion chamber when the piston is at top dead center. A smaller clearance will increase the compression, generally resulting in more power.

You need a minimum clearance so the piston does not wack the cylinder at high rpm.

As cuinrearview mentioned you can't change the squish (at least not with some fancy machine work) on a MS291. The 291 is what's known as a "clamshell" motor.

On other saws, that use a base gasket, you can lower squish by using a thinner base gasket or eliminating it. You can also remove some material from the bottom of the cylinder to get the same effect.