| 摘要 |
PURPOSE:To limit the over speed of the engine, by using a weak valve spring for an intake valve so that the operation of the valve is made out of order at a high speed, and as well to prevent an exhaust valve from sticking, by using a strong valve spring for the exhaust valve. CONSTITUTION:The distance HIN between a cylinder head and a spring retainer 14 on the intake valve 14' side is set to be larger than the distance hEX between the cylinder head and a spring retainer 14 on the exhaust valve 11 side, and the set load of a valve spring 12 for the intake valve 10 is smaller than that of a valve spring 13 for the exhaust valve 11. The intake valve is liable to generate jumps, bounces and surging so that the operation of the intake valve is made out of order at a high speed, thereby the overspeed of the engine may be prevented. The exhaust valve is closed under large set load, and therefore such a possible risk that sticking is brought about is avoided. |
