Cb250 compression?

Hey dudes.

I've played around with the head gasket thickness of my air cooled ohc 223cc (referred to as a cb250) engine. The performance has gone down. It has a 3 layer gasket so I removed 2 layers, started it and I think the valves were just hitting the piston. Only by a fart though. So I put a second layer of the gasket back in and it started up fine but is boggy in the top end and when I change up gears. I want to test the compression to see if the valves might be slightly bent. Does anyone know the compression I should expect to see if I do a compression test? Has anyone out there done a compression test on this type of engine? Any good help will be appreciated.

Gus.