hi i have got a nitrotek lightening stike brushless. i took it out today and it was all going well, after i got home i was gonna have another go with it. plugged the battery on and tried to set off but it would not go, the motor sounded to be turning but was not producing any drive. i took the motor off to see what had happend. it revs under no load but when any load is put on it the motor shaft doesn't turn but the motor sounds to turning? any idea what it is and if it is fixable?