If you are intersted in a razor dirt rocket bike, check out this video I found.
These are modified MX500′s and this is according to the video producer.
“2 years ago The 750w motor I got was a direct bolt in. But, if you do nothing else but a 750w motor, you will see minimal difference form stock. To get more snap, you need a 50 amp controller. To get more speed you need to add a battery and go to 48v. (*If you stay 36v, get a 36v/50a controller, if you go 48v get a 48v/50a controller)”
So this is just example of a project you can do with a razor dirt rocket bike. I have seen some other video’s where they speed tested these little suckers up to over 40 MPH. Pretty cool!