If you want to know what you have, you can yank the head off and measure the bore with veneers and measure the stroke of the crank. Than you can pull your reeds out to take a look at the intake and see if any porting was done. Your exhaust ports could have been raised. You could have sleeves in the cylinders. Wont know unless you look. If your not real mechaniclly inclined, fuckin leave it alone and beat the shit out it! good luck.