| 摘要 |
PURPOSE:To aim at making the wall thickness of an engine cylinder uniform in a two-cycle engine which incorporates a main exhaust passage and an auxiliary exhaust passage disposed therein with an auxiliary valve, by making the shaft part of the axiliary valve pierce through and project from the cylinder head, and by coupling a drive device to the projecting end of the shaft part. CONSTITUTION:There are provided a main exhaust passage 7 communicated to a main exhaust port 5 of a cylinder 6 and two auxiliary exhaust ports 8, 8 in the cylinder 6 on the circumferentially sides of the main exhaust port 5. The auxiliary ports are communicated with the main exhaust passage 7 through the intermediary of an auxiliary exhaust passage 9 in which an auxiliary valve 10 adapted to be rotated (opened and closed) in accordance with variations in the rotational speed of an engine is disposed. In the above- mentioned two-cycle engine, the axial direction of the auxiliary valve 10 is set in the sliding direction of the piston, and the shaft part 10d of the valve 10 is made to pierce through and project from the cylinder head 1, and is coupled to a transmission device 12 in a drive device 11.
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