i hope im posting this in the right area? anyway i played with pocket bike motors a lot & heres a great link to engines with lots of mod stuff, tuned exaust, hot heads,reed kits.carbs & lots of other goodies to twiddle with!http://www.pocketbikesunlimited.com/ it gives one lots of great ideas!ps my 49 cc pocket bike does about 40 with mild mods!!