| 摘要 |
PURPOSE:To improve utilization efficiency of cooling water by placing an exhaust valve on the lower side of a cylinder head and an intake valve on the upper side thereof respectively, in an engine provided with water jackets communicating into said cylinder head from the circumference of a cylinder. CONSTITUTION:An intake valve 10 is placed on the upper side of a cylinder head 8 exhaust valve 11 is placed on the lower side thereof respectively, and an intake passage 12 is formed on the upper side and an exhaust passage 13 on the lower side respectively. And around a cylinder 1, a cooling water jacket 16 is formed and on the cylinder head 8, a cooling water jacket 17 surrounding the exhaust valve 11, exhaust passage 13, intake valve 10 and the intake passage 12 is formed respectively. A room 25 is formed above the intake valve 10 of the cooling water jacket 17, and a thermostat 19 is placed in the room 25. And a cooling water inlet 26 is formed on the end portion nearest to a crank shaft 5 at the lower end of the cooling water jacket 16, and a discharge port 35 of a water pump 27 is communicated to the cooling water inlet 26.
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