Step 1: Unscrew the screws that fix the upper cover of the motor, and open the motor cover. Unscrew the screws use for balance that between the small belt and the top of motor, and then remove the screws that fix the motor base to the frame.
Step 2: Remove the screws that fix the motor base, replace it with a new motor and fix the base to the new motor, and fix the motor base to the frame.
Step 3: Adjust the small belt in a straight line, and tighten the motor screw that fixes the small belt until the small belt is turned by hand to 45 degrees. Then tighten the screw for balance of the motor to make sure the top of the motor is in balance.
Step 4: Put on the motor cover and tighten the screws that fix the motor cover.