Rudy's mouth stops moving properly because the round white drive gear in the head has broken teeth.

Rudy's mouth gear has broken teeth: rotate it to use the good section

Cause: The original gear wears and loses teeth. Several owners found the black replacement gears are slightly larger and jam against the mating gear.

Checks

• Open the head and inspect the round gear and the arched gear it drives for missing teeth.
• If fitting a replacement gear, turn it by hand through the full range to check it does not bind.

Fix

• Reinstall the original gear rotated so the damaged section sits outside the range the mouth actually uses.
• Alternatively, rebuild the missing teeth with two-part epoxy and file them to shape.

Systems

• WPC Alpha-Numeric

Games

• Funhouse

Related tips

• Trap door doesn't always stay up on the first try: worn lift crank

Source: Pinball Repair help group!! (Facebook group)