If Marty's arm does not move freely, the arm gear may have been tightened too much during assembly, causing it to jam. Loosening the gear can allow the arm to move again.

Loosen the arm gear

Turn Marty off before adjusting the arm gear.

  1. Loosen the upper arm gear screw by turning it anticlockwise, as shown in the demonstration below.
  2. Pull the upper arm gear slightly away from the body until the arm moves freely.

Loosening the upper arm gear screw and moving the gear slightly outwards

The demonstration shows an arm that is jammed by an overtightened gear, then moving freely after the screw is loosened and the gear is eased outwards.