What was found
HELICOPTER LOST ENGINE POWER IN-FLIGHT. DURING GROUND RUN TROUBLESHOOTING PROCESS, THE ENGINE WOULD NOT OPERATE ABOVE 1500 RPM. THE MARVEL SCHEBELER (MODEL MA-6AA, SN AH-1-383) CARBURETOR WAS BENCH TESTED BY THE NTSB AND WOULD ONLY PERFORM APPROXIMATELY 50 PERCENT CAPACITY. DURING CARBURETOR TEAR DOWN INSPECTION, FOUND PLASTIC RESIN ADHESIVE MISSING. THIS ADHESIVE LOCKS THE BELLOWS TO THE SHAFT ON THE AUTOMATIC MIXTURE CONTROL (PN 293-548). THIS ALLOWED THE BELLOWS TO MOVE DOWN THE SHAFT, THEREFORE, LIMITING FUEL OUTPUT.