What was found
RPM COULD NOT BE REDUCED BELOW 2,000 RPM IN-FLIGHT, NECESSITATING POWER-OFF LANDING. INSPECTION REVEALED THE CARBURETOR ACCELERATOR PUMP DISCHARGE TUBE HAD COME LOOSE AND LODGED IN THE THROTTLE VALVE PREVENTING FULL CLOSURE OF THROTTLE. THE OVERHAUL MANUAL SPECIFIES THE TUBE IS HELD IN PLACE WITH LOCTITE ONLY. SUBMITTER RECOMMENDS REDESIGN SO THE TUBE IS MECHANICALLY HELD IN PLACE OR ELSE A REGULAR INSPECTION INTERVAL TO DETERMINE IF THE TUBE IS LOOSE. ENGINE TT: 3,882 HOURS. ENGINE TSOH: 1,714 HOURS.