| 摘要 |
PROBLEM TO BE SOLVED: To provide a small and light decompression device by positively releasing decompression operation, when the number of engine revolution exceeds the prescribed one. SOLUTION: A decompression device for a four-cycle internal combustion engine is provided with a shaft hole 21 formed on a cam axis 1, a hydraulic pressure chamber 30 formed in the shaft hole 21, a decompression axis 25 reciprocable according to hydraulic pressure in the hydraulic room 30, a decompression pin 24 which drives to open an exhaust valve in the stage of compression in the first position of the decompression axis 25 and stops the drive for opening the exhaust valve in the second position, a hydraulic control valve 32 while opens and closes a leak hole 33 interlocked with a weight 35, which rotates according to the number of engine revolutions, and controls hydraulic pressure of the oil pressure chamber 30.
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