When an AC motor is sluggish due to carbon buildup, a motor burn may restore the motor to its prior speed and power. The idea is to run the motor at top speed for 4 to 5 minutes. Release the handwheel brake to enable the motor only to turn the handwheel - not the entire machine. Clamp the foot control at top operating speed. You may need to manually turn the handwheel to get the motor started, but eventually it should begin to run slowly. Watch for sparks and/or smoke from the motor. DO NOT LET IT CATCH ON FIRE. The motor should gradually speed up as the carbon on the armature burns off.