I found out what was causing the MP III to cause so much resistance: the tire was slightly rubbing against the left of the rear bike frame.
I was initially trying to determine whether it was a mechanical or an electrical problem, which is why I asked the following question:
Is there and mechanical noise as well as the vibration, like a tyre or brake pad binding?
As it was only rubbing after hard braking, and became easier after pressing the throttle, you must have somehow neglected to tighten the left hand axle nut properly which would have allowed the wheel to move slightly within the dropout on the left hand side when it was subjected to braking and acceleration forces.
If the axle nut had been tightened properly with the wheel incorrectly aligned and touching against the frame, the resistance caused by the rubbing tyre would have been more consistent as it would not have been greatly affected by braking or accelerating.
With these motors it is very important to make sure that both of the axle nuts are correctly tightened, or the tremendous torque being transmitted through the axle will cause the axle to spin within the dropouts and damage the wiring harness that is attached to centre of the motor.
Anyway, I'm glad you were able to locate and rectify the problem, I just hope you managed to do it before it wore right through the side of the tyre.
Alan
