| 摘要 |
PROBLEM TO BE SOLVED: To reduce the size and the weight of an engine by a method wherein parts in a cylinder head are mounted in a compact manner by optimizing the shape of an ignition plug hole. SOLUTION: A cylinder head S is divided at a division part 1 into upper and lower heads S1 and S2. Upper and lower ignition plug holes 21 and 12 are formed in the respective heads. A lower ignition plug hole position is set based on the installation position of an ignition plug P. An upper ignition plug hole position is set in a state to be offset from the lower ignition plug hole 12 based on arrangement of each constitution element mounted in the upper head. Connection is effected such that each ignition plug hole has a taper part formed at the division part 1 or the lower ignition plug hole 12 is increased in diameter to surround the upper ignition plug hole 21.
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