changing the piston has its own set of advantages and disadvantages. Higher compression can lead to more power and a rippin motor, but can also lead to pinging/detonation (especially with lower octane fuels), jetting problems, overheating problems, and more than likely you will need to change your timing. You might consider having head modifications done and blueprinting the motor. These are spendy options, I know, but they last (unlike the piston that is good for an alleged 15 hours) and always make power. These options also create a smoother, more reliable, more effiecient, more powerful motor and should always be considered when racing. Pretty much anything that you can do to a car motor, you can do to your bike motor. If you want more power, get an exhaust, drop a tooth on the rear sprocket, or go supernuts and get a bigbore kit. These are cost effective too, sort of. Just my $0.02