| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of part items and to improve cooling efficiency of the cooling structure of a water-cooled engine by reducing external piping for cooling water passage. SOLUTION: Each of a cooling water passage 11 of an exhaust pipe 3 and a cooling water jacket 12 inside a cylinder 1 is divided in two. Cooling water is introduced into one of a cooling water passage 11a of the exhaust pipe 3. A cooling water circulation passage is provided, such that the water introduced into the one cooling water passage 11a goes through one of the cooling water jackets 12a in the cylinder 1, a cooling water jacket 13 in a cylinder head 5, the other cooling jacket 12b in the cylinder 1, and the other cooling water passage 11b of the exhaust pipe sequentially, to be led into a cooling water passage 14 of an expansion tube 7.
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