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.
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