TM 5-4240-501-148PCARBURETIONAutomatic ChokeFig. 15 -- Inserting Choke LinkMove choke plate to an over center position as shown inFig. 16. Tighten carburetor mounting screws in astaggered sequence. Please note Opening the choke toan over center position places the diaphragm in apreloaded condition.Move choke plate to a normal position. Choke plateshould now fully close, Fig. 16.If choke valve is not fully closed, check to be sure chokespring is properly assembled to diaphragm, and alsoproperly inserted in its pocket in the tank top. Installchoke link cover and gasket.Fig. 16 - Pre-Loading DiaphragmAll carburetor adjustment should be made with the aircleaner on engine. Best adjustment is made with a fueltank half full of gasoline.To Adjust Carburetor:1.Start engine and run long enough to warm it tooperating temperature.NOTE: If engine is out of adjustment sothat it will not start, close the needlevalve by turning it clockwise. Then openneedle valve 1-1/2 turnscounterclockwise. Fig. 17.Fig. 17 - Adjusting Carburetor2. Move speed control lever to run engine at normaloperating speed.a.Turn needle valve in clockwise until engine startsto lose speed (lean mixture).b.Then slowly turn needle valve outcounterclockwise past the point of smoothestoperation until engine just begins to run unevenly(rich mixture).c.Turn needle back clockwise to midpoint(smoothest operation) between rich and leanmixture.d.Final adjustment of the needle valve should beat the midpoint between rich and lean.3.Move engine to SLOW. Turn idle adjusting screwuntil a fast idle is obtained 1750 R.P.M.If the engine idles at a speed lower than 1750R.P.M., it may not accelerate properly. It is notpractical to attempt to obtain acceleration fromspeeds below 1750 R.P.M., since the richer mixturewhich would be required, would be too rich fornormal operating speeds.7
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
