is the on/off toggle switch broken? i would get a continuity tester and check to make sure that it works properly. it really doesnt sound gear related. can you describe the problem further? does it still work at slow speeds? if it doesn't it could be that the switch is fine and that the motor is on it's way out. any funny smells? does it run differently when first started vs after some heavy use? older kitchenaid mixers are worth a repair job hang in there. try some experiments and get back to me.