6-
6
AUTOMATIC DECOMPRESSION
SYSTEM
The decompression system operates to release compression by lifting up the exhaust
valve at starting.
,”
The release lever mounted on the camshaft has a flyweight at one end and
a
crescent
cam
at
the other end. When starting the engine, the crescent cam juts out from the
exhaust
.
cam.
The exhaust tappet rides
over
the crescent cam opening the exhaust valve to release
compression.
CRESCENT
EXHAUST
FLYWEIGHT
CAM
CAM
TAPPET
2LtL
l/
RELEASE LEVER
/
EXHAUST CAM
SNAP RING
CAMSHAFT
FIG.
77
,--
When the crank
speed
reaches
a
certain revolution, the flyweight
of
the release lever
moves outward by the centrifugal force turning the release lever to retract the crescent
cam. Thus the exhaust valve closes allowing a sufficient compression for the engine to
start up.
‘FLYWEIGHT
LEASE LEVER
SNAP RING
CAMSHAFT
FIG.
78
The components
of
the decompression system are different by
“D”
type and
“B”
type
engines, however the principle of operation is the same.
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