7.
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 CAM
EXHAUST CAM
LEVER
Fig.
7-1
a
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 below the crescent cam. Thus the exhaust valve
closes allowing a sufficient compression for the engine to start
up.
FLYWEIGHT
CRESCENT
CAM
Fig. 7-2
LEVER
-43-
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