sounds like you either overgeared it and burnt out the motor, or you burnt out the ESC. I take it your a newbie and dont have a 4 cell pack. I'd say try running the motor through your battery (direct connection) and see if it runs. Check and make sure your brushes are still good, see how the com is, clean out the motor. Also try your old motor again and see if it works, if it doesnt, it syour ESC. Can your ESC handle a hot modified motor? give me more details man.