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7. AUTOMATIC DECOMPRESSION SYSTEM
7-1 FUNCTIONS AND MECHANISM
The decompression system is installed on the cam in order to open the intake valve and relieve the
compression pressure at the first half of the engine compression cycle. The flyweight installed inside the
cam gear has an appropriate shape (weight) to have the effect of the centrifugal force, and the end of the
rotary shaft has a crescent cam shape. Since the gravity force on the weight is larger than the centrifugal
force on the weight at the low cam gear revolution when starting, the crescent cam projects the cam
profile and lifts up the follower of the cam lifter, opens the intake valve.
FLYWEIGHT
CAMLIFTER
CRESCENT
CAM
ROTA
TION
When the engine is running, the crescent cam is retracted into the camshaft profile because the centrifu-
gal force applied onto the flyweight becomes larger than the gravity force and the decompression turns
OFF.
7-2 INSPECTION
(1) When assembling the cam gear assembly, be sure that the spring hook is hooked on the flyweight.
(2) Be sure that the flyweight moves smoothly.
FLYWEIGHT
CAMLIFTER
CRESCENT
CAM
ROTATION
Fig. 7-1
Fig. 7-2
Содержание EH025
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