Squish band questions

[nickaloadien]

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?

 

[ImpulseRocket]

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?

I will refrain from expositing a ton of information on what "best" is. This post of mine on a thread on this very subject from just a couple of weeks ago breaks down the basics of your question

Real life consequences re: squish gap

A few light swipes across the 120 will give you a quick indication on where the high spots are, once the high spots are level, then it's a matter of sanding a bit and measuring, sand a bit, measure, sand a bit, measure, you get the picture. Probably a full six pack job. That's basically exactly...

motoredbikes.com

The gap is just one aspect of effective squish though. The other is the shape of the squish band in relation to the piston itself. The idea of a tight squish band is to "squeeze" the intake charge into the center of the combustion chamber and if either is shaped incorrectly it can actually cause performance to decline instead of improve.