TM 5-4240-501-148PCARBURETIONAutomatic ChokeFig. 8 - Style of Carburetors (Cont’d.)AUTOMATIC CHOKEMODEL SERIES 92000, 94000,110900, 111900The automatic choke operates in conjunction with enginevacuum, similar to the Pulsa-Jet fuel pump.A diaphragm under the carburetor is connected to thechoke shaft by a link. See Fig. 9. A calibrated springunder the diaphragm holds the choke valve closed whenthe engine is not running.Fig. 9 - Automatic Choke SystemUpon starting, vacuum created during the intake strokeis routed to the bottom of the diaphragm, through acalibrated passage, thereby opening the choke.This system also has the ability to respond similar to anacceleration pump. As speed decreases during heavyloads, the choke valve partially closes enriching themixture, thereby improving low speed performance andlugging power.The automatic choke can easily be checked to determineif 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 befully closed.2.Move the speed control to the stop position; -thegovernor spring should be holding throttle in a closedposition. Pull the starter rope rapidly. The chokevalve should alternately open and close.4
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