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ROCKER ARM
(EXHAUST)
ROCKER ARM
(EXHAUST)
ROCKER ARM
(INTAKE)
CAM
CRESCENT CAM
RELEASE LEVER
RELEASE LEVER
ROCKER ARM
(EXHAUST)
ROCKER ARM
(INTAKE)
CAM
CRESCENT CAM
CAMSHAFT
ROCKER ARM
(EXHAUST)
CAMSHAFT
RELEASE LEVER
RELEASE LEVER
DETAIL
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DETAIL
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Fig. 11-2
11. AUTOMATIC DECOMPRESSION SYSTEM
11-1 FUNCTIONS AND CONSTRUCTION
EX series engines employ an automatic decompression system as a standard feature. This enables easy
starting of the engine, with lighter recoil pull.
The automatic decompression system releases the compression of the engine by lifting up the exhaust valve at
cranking speed. The following is the explanation of the function.
At the end of the compression process, the release lever lifts up the rocker arm (exhaust) which in turn opens
up the exhaust valve slightly to release the compression.
The release lever has a flyweight on its end and another end of the lever is a crescent cam.
When the engine is cranked, the crescent cam projects above the cam profile and lifts up the rocker arm
(exhaust) because the force of the return spring on the weight is larger than the centrifugal force on the weight.
When the cranking speed reaches a specified r.p.m., the crescent cam is retracted under the cam profile
because the centrifugal force applied to the flyweight becomes larger than the force of the return spring on the
weight and thus it is shifted to the position shown in the illustration below.
Fig. 11-1
11-2 INSPECTION
When assembling the release lever, make sure that it works smoothly.