Introduction to Razor Motors
cork,
The 1/3 was a typo and should have been 3/4. I've corrected it up above. The heat comes from the lost power in the windings. (I^2 * R(winding))
As for the motors, the distance between the holes is the same. Even the Razor motor has a different screw size and case diameter than the Speed 300 motor.
Regards.