Fig. 15 -- Inserting Choke Link

TM 5-4240-501-148P CARBURETION Automatic Choke Fig. 15 -- Inserting Choke Link Move choke plate to an over center position as shown in Fig. 16. Tighten carburetor mounting screws in a staggered sequence. Please note Opening the choke to an over center position places the diaphragm in a preloaded condition. Move choke plate to a normal position. Choke plate should now fully close, Fig. 16. If choke valve is not fully closed, check to be sure choke spring is properly assembled to diaphragm, and also properly inserted in its pocket in the tank top. Install choke link cover and gasket. Fig. 16 - Pre-Loading Diaphragm All carburetor adjustment should be made with the air cleaner on engine. Best adjustment is made with a fuel tank half full of gasoline. To Adjust Carburetor: 1. Start engine and run long enough to warm it to operating temperature. NOTE: If engine is out of adjustment so that it will not start, close the needle valve by turning it clockwise. Then open needle valve 1-1/2 turns counterclockwise. Fig. 17. Fig. 17 - Adjusting Carburetor 2. Move speed control lever to run engine at normal operating speed. a. Turn needle valve in clockwise until engine starts to lose speed (lean mixture). b. Then slowly turn needle valve out counterclockwise past the point of smoothest operation until engine just begins to run unevenly (rich mixture). c. Turn needle back clockwise to midpoint (smoothest operation) between rich and lean mixture. d. Final adjustment of the needle valve should be at the midpoint between rich and lean. 3. Move engine to SLOW. Turn idle adjusting screw until a fast idle is obtained 1750 R.P.M. If the engine idles at a speed lower than 1750 R.P.M., it may not accelerate properly. It is not practical to attempt to obtain acceleration from speeds below 1750 R.P.M., since the richer mixture which would be required, would be too rich for normal operating speeds. 7