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TM 9-8000
Figure 4-73. Velocity-Vacuum Governor-Type I.
b. Velocity-Vacuum Governor - Type II.
excessive speed reduction.  To prevent this, an extra
second type of velocity-vacuum governor (fig. 4-74) also
compensator spring is fitted to offer additional resistance
to throttle valve closing during periods of small throttle
uses a spring to pull the throttle valve toward the open
position.  One end of the spring is attached to the
carburetor housing through an adjusting screw.  The
(4)  By loosening or tightening the engine speed
other end of the spring is attached to the throttle shaft
adjusting screw, the maximum engine speed can be
through a flywheel that is attached to the end of the
adjusted. The screw accomplishes this by changing the
shaft.  A compensator spring is located so that it
tension of the governor spring.
operates with the throttle shaft during periods of small
throttle openlng. Operation is as follows:
4-35.  Centrifugal-Vacuum  Governor  (Fig. 4-75).
(1)  As engine speed increases to the governed
A centrifugal-vacuum governor consists of two units that
maximum, the speed of the mixture forces the throttle
work together to regulate maximum engine speed. One
valve toward the closed position against the force of the
is the centrifugal unit that is mounted under the Ignition
governor spring.
distributor. The other is the vacuum unit that is mounted
under the carburetor.
(2)  The flywheel, by inertial force, prevents
fluctuation of the throttle valve that would occur due to
a. Centrifugal Unit. The centrifugal unit is driven by
pulsation of the intake mixture caused by the time
the engine at the Ignition distributor drive. Its purpose is
between, or the overlapping of, the intake strokes.
to control the vacuum unit based on engine speed.
Operation is as follows:
(3)  During periods of light loads, the engine
can reach Its maximum governed speed with a relatively
small throttle opening.  This could cause the intake
mixture to close the throttle valve too much, causing


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