Fairly easy project to put this on a Razor MX500. It hits around 30 miles an hour with my 10 year old driving. Only gripe is that there does not seem to be a slow speed. Slowly twist the throttle, and about half-way, the motor suddenly engages and jerks fairly hard. The throttle allows 15 mph to 30 mph. Going less that 15 and my son needs to rev the throttle in bits. He is good at it and we are very happy with the conversion, but a nice, easy gradual throttle would be nice. If anyone has a fix for this issue, please let me know.