Simplest thing to do is put a compression gauge on it.

Make sure the cylinder is wet. Not dry.

On some models--you can mill a few thousanths (.001--.008) off the bottom of the cylinder head and raise the compression. There is a point where you go to far and then the piston hits the top of the cylinder. KABOOM!!

But, nothing comes free. When you drop the cylinder--you increase the compression and increase the intake duration (provided it's a piston ported design). Increasing the intake is good--ya get more fuel in.

But, at the same time--you are decreasing the exhaust duration. This is major BAD. Especially on a 2-stroke engine. Getting the spent exhaust gas out the port is crucial. Lowering your exhuaust duration is going to kill any performance gains from increased compression and intake duration.

So--then you find yourself grinding on the exhuast port to take at least as much off the top as you took off the bottom of the cylinder. And thats just to get it back to where it was to start with. If you want to increase the exhaust duration beyond what it was to start with--probably a good thing--then you'll have to take off even more from the top of the port.

How you go about grinding off the exhaust port and raising it up without ruining the chrome plating has always been a mystery to me. Some guys will say that a special rotary (carbide) bit in an air powered die grinder will do the job. Others say that disturbing the chrome plating in any way will lead to it peeling off in short order.[]

I've never tried it with a gas engine. I want to--but I'm scared that I'll ruin a cylinder.

Best engine to experiment with--probably a Ryobi 31cc or a Homelite 25. They are cheap and readily available. For $60 you can buy a NIB weed eater.