I'm not to up on compression ratio, can anyone explain this to me? I see some bikes are 10:1 other are 9:1 which is better?

 

The higher the compression ratio the more torque it puts out. t 9:1 and 10:1 are about standard for about any quad unless its high performance or modified then it would be 12:1-13:1. Once you gety this high in compression you have to use higher octane fuels.