| 摘要 |
PURPOSE:To reduce the content of HC in exhaust gases at the time of a no-load or a low load operation by alleviating the cooling of a cylinder head and a cylinder or heating cooling air in said operation condition. CONSTITUTION:Cooling wind generated on a cooling wind fan 4 connected directly to a crankshaft 11 passes a cooling wind supply duct 5 and cools a cylinder and a cylinder head. A changeover valve 6 provided in way of the duct 5 turns about a hinge 7 and is set to 'A' position at the time of medium and high load operations, thereby supplying cooling wind to the cylinder and the cylinder head. When an engine is in no-load and a low load condition, the valve 6 is set to 'B' position, thereby shutting off wind supply to the cylinder and the cylinder head, and exhausting to the atmosphere.
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