i have one of these bikes but mine is all modded(pipe,deck height,piston and rings,carb,velocity stack and gearing)mine does about 55mph with my 200lb azz on it.they are alot of fun until you get pulled over.

and your speedo should actually be rpms of the motor not mph but the china man who made it doesn't know the difference.check out pocketbikesunlimited.com for parts they used to have everything for these bikes