Once you over heat a motor really good for what ever reason, I mean cook it, you detroy the coating on the windings and they will always run hot and eventually thermal. Hate to say it but you may have a practice motor as they will run fine for 5 to 7 minutes but the temps will continuously keep creeping up. Open it up if the windings on the stator are discolored (they will look blue/grey kinda like a black and blue on your arm).