just spent a while you tube'n some cars with bike motors, they are all in very small cars usually with perspex windows and other extreme weight loss programs, and they all seem to love doing wheelspin/donuts... in fact none of them look very fast, they are loud and chew through gears quickly so they sound very fast.

None of them seem to be able to get the things high in the revs without wheelspin, and of course when the wheels are spinning there is minimal load on the motor which is allowing the high revs