built to sprint from the back of the pack to the front when I'm blocking during group rides. this is my favorite bike. still using pa50II reed block with boysen 2 stage and a opened up 50II intake to an exhaust header for carb mounting.notched veriator with pa50I weights . indigan bars and a chopped and dropped puch seat pan with a crafting foam seat pad... bike does high 50'S all day long . top gps'd speed 63.9. the head stock has been turned to accommodate for the larger piston.