| 摘要 |
PROBLEM TO BE SOLVED: To improve a valve system character and ensure durability. SOLUTION: In this valve system, a valve spring 7 is constituted of a first valve spring 17 positioned at a valve head 9 side and a second valve spring 15 provided in series with the first valve spring 17 and positioned at the other end side of a valve. The second valve spring 15 is formed of a lighter material compared with the first valve spring 17, and the second valve spring 15 is lighter in weight than the first valve spring 17.
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