Originally posted by Matthew Cotten
Your magnets are a little weak sounds like.
Let me add a little explanation. The rotating magnetic field from the rotor generates the voltage in the stator that is sensed by ESC (that's how the ESC knows the position of the rotor for the right timing). When magnets are weak the response is so weak, that it gets lost in the electric noise and can't be sensed by ESC any more.
Right answer: Stronger magnets in the rotor.