This thing has a 43cc engine on it. It is basically a weed wacker engine. It was originally 1 wheel drive and geared way too high. I wanted it slow enough that I could run as fast as it could go. I removed the left undriven wheel and axle. I replaced the the right wheel with a sprocket. I extended the frame adding a solid axle, wider tires and a better brake. Reduction is 5:1 lower than the original gearing. The engine can wind out more though so speed was reduced maybe 1/2 with me on it. With my daughter on it, it is RPM limited, not power limited. It hits top speed almost instantly though. I also added a floor pan. She started out just driving mostly in circles, but she figured out drifting on her own so I have to get a seat belt in it and add a cage. I will also add a remote kill so I won't have worry if I can catch her on foot.