Honda Minimoto Maxii 400

Hey guys, I just picked up minimoto maxii off craigslist that didn't work. Well, I got it stripped down to see whats wrong with it. I knew the throttle was broken for sure when I got it, I was almost sure the battery was no good (apparently the bike sat for 2 years, maybe longer) The battery was reading 15.8 volts, so yea, thats junk. I already had a 36v scooter, so I was able to pull out the battery and use that to test the rest. the controller works, cause as soon as I plugged it in the motor kicked on. The motor is toast though, bearings are shot, someone was riding this thing with the chain WAY too tight.

So my question is, can I buy a 36v 500w motor (they no longer make the OEM 400w motor) and mix that with the stock 36v 400w controller? Or would I have to get a new controller as well? Thanks again!