Squish clearance question

[theguy2024]

What size should my 100cc/79cc china engines squish clearance be? I heard the minimum has to be .7-.9mm but does that mean it can be higher? what is best number for performance?

 

[Larry Trotter]

It’s there to create turbulence in the combustion chamber. Some designs don’t use it at all but in general less clearance is better. Here’s a couple of heads with different designs one fairly open one with a squish band.