| 摘要 |
PROBLEM TO BE SOLVED: To provide a decompression device for an engine, capable of suppressing the early wear of a slipper surface of a rocker arm and reducing wear of the cam crest surface. SOLUTION: Centrifugal force acting on a flyweight 18 is small till the engine reaches prescribed engine speed and the flyweight 18 is maintained, in an abutting state on a stopper pin 20 by energizing force of a return spring 21 (Figure 3 (A)). At this time, a cylindrical outer peripheral part 17a of a decompression cam 17 projects only slightly from a cam surface 13a for exhaust and abuts on the slipper surface of the rocker arm, an arm end part on an opposite side is pushed down and an exhaust valve is slightly opened, and thereby cylinder pressure is reduced. When the engine reaches a prescribed engine speed, centrifugal force acting on the flyweight 18 becomes large, the flyweight 18 is extended and opened against energizing force of the return spring 21, and the decompression cam 17 is stored within the cam shaft 7 (Figure 3 (B)), thereby the exhaust valve performs a normal valve operation.
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