Carburetor Adjustments

CARBURETION - TM-5-4240-501-14P_122

CARBURETION L. P. Fuel Governed Idle

TM-5-4240-501-14P Special Diver Air Support System (SDASS) NSN 4220-01-292-3708 Manual
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TM 5-4240-501-14&P Fig. 105 - Assemble Fuel Pump Install main nozzle using blunt screw driver to prevent damage to slot and metering hole. Place bowl on carburetor and install bowl nut and washer. Install one (1) pump valve spring on spring boss, Fig. 106, and then place diaphragm on carburetor. Put pump spring cup and pump spring on diaphragm, Fig. 105. Place a pump valve spring on spring boss in pump body, Fig. 106, and place pump body on carburetor. Place damping diaphragm, pump gasket and pump cover on pump body and install three (3) screws. A fuel pump repair kit is available, see illustrated parts list for part number. Fig. 106 - Pump Spring Location (Valve Flap Bent Down for Clarity) Place choke shaft in carburetor body and slide in choke valve with notch out and dimple down toward float bowl, Fig. 107A. Install two (2) screws using a screw driver. Slide in throttle shaft and then slide in throttle plate with two (2) dimples facing toward the idle valve. When valve is installed correctly, the dimples will be down and the number on the plate visible with the throttle in the closed or idle position, Fig. 107B. Install the idle and-high speed needle valves. CARBURETION Cross-Over Flo-Jet Fig. 107A- Fig. 107B- Carburetor Adjustments INITIAL ADJUSTMENT - Turn idle and needle valves clockwise until they just close, Fig. 108. CAUTION: Valves may be damaged by turning hem in too far. Now open high speed needle valve ll/2 turns counterclockwise and idle valve one turn. This initial adjustment will permit the engine to be started and warmed up prior to final adjustment. Fig. 108 - Carburetor Adjustment NOTE: Carburetor adjustments should be made with the air cleaner on engine. FINAL ADJUSTMENT PROCEDURE Idle Valve Mixture Place governor speed control lever in "IDLE" position. Set idle speed adjusting screw to obtain 1750 R.P.M. minimum while holding throttle lever again screw. Turn idle valve in until R.P.M. slows or misses (clockwise - lean mixture), then turn it out past smooth idling point until engine runs unevenly (rich mixture). Now turn idle valve to the midpoint between rich and lean so the engine runs smoothly. Release throttle lever. 29

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