I know that ICARE-RC sells them, but as for repair.... unknown. Another possible cause could be that a mounting screw was screwed in too far, and damaged the windings. This is known to cause poor performance and rapid heating of the esc and/or motor. Me thinks the previous owner got a bit careless, then sold the system on to some unsupecting person; you. If the windings are damaged though, the cost of repair would be more than the motor cost you to begin with, since its not a simple task to to remove & replace them....