| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive and sufficient cooling effect without requiring complicated and large-scaled repair/change for molding a water jacket and without adding a complicated control. SOLUTION: A cooling passage 19 for cooling heat from an exhaust port 3 by passing cooling air through the inside is formed from end to end of a cylinder head 2 so as to cross between each cylinder by core molding or machining between a mounting surface of a rocker cover gasket 17 of a cylinder head 2 of an engine 1 and the exhaust port 3. Both ends of the cooling passage 19 are connected with nipples 19a and 19b. The one nipple 19a is connected with an upstream side of an air cleaner 8 and the other nipple 19b is opened in the atmosphere. As a result, when intake of the engine 1 is performed, intake from also the other nipple 19b is performed by intake negative pressure of the upstream side of the air cleaner 8 and the intake air passes the cooling passage 19 and becomes cooling air to remove heat.
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