Fig. 8 - Style of Carburetors (Cont’d.)

TM 5-4240-501-148P CARBURETION Automatic Choke Fig. 8 - Style of Carburetors (Cont’d.) AUTOMATIC CHOKE MODEL SERIES 92000, 94000, 110900, 111900 The automatic choke operates in conjunction with engine vacuum, similar to the Pulsa-Jet fuel pump. A diaphragm under the carburetor is connected to the choke shaft by a link. See Fig. 9. A calibrated spring under the diaphragm holds the choke valve closed when the engine is not running. Fig. 9 - Automatic Choke System Upon starting, vacuum created during the intake stroke is routed to the bottom of the diaphragm, through a calibrated passage, thereby opening the choke. This system also has the ability to respond similar to an acceleration pump. As speed decreases during heavy loads, the choke valve partially closes enriching the mixture, thereby improving low speed performance and lugging power. The automatic choke can easily be checked to determine if it is or is not functioning properly. 1. Remove the air cleaner and replace the stud. Observe the position of the choke valve; it should be fully closed. 2. Move the speed control to the stop position; -the governor spring should be holding throttle in a closed position. Pull the starter rope rapidly. The choke valve should alternately open and close. 4