| 摘要 |
A four-stroke internal combustion engine in accordance with the present invention comprises a piston, a valve chamber, a crankcase, an oil chamber separated from the crankcase, and an oil mist feeding passage extending from the oil chamber to the crank case via the valve chamber for supplying oil mist in the oil chamber. The oil mist feeding passage has a first passage extending from the oil chamber to the valve chamber, a second passage extending from the valve chamber to the crankcase, and a third passage extending from the crankcase to the first passage. The first passage has a first opening directed toward the oil chamber. The second passage has a second opening directed toward the crankcase located at a point where it can be closed by the piston when it travels downwardly. The third passage has a third opening directed toward the crankcase located at a point below a bottom dead center of the piston. The engine further comprises a first check valve provided in the oil chamber and which allows atmospheric air to flow into the oil chamber, and a second check valve provided in the valve chamber and which allows gas to flow toward an intake side of a carbureter.
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