| 摘要 |
PURPOSE:To prevent the malfunction of a valve by causing an exhaust timing control valve that opens and closes the upper edge of the exhaust port of a two-cycle engine to operate once from its fully opened position to its fully closed position when the engine speed is increased by more than a fixed rotational frequency from the idling engine speed. CONSTITUTION:An exhaust timing control valve that opens and closes the upper edge of the exhaust port of a two-cycle engine obtains from a control unit 4 output signals of a fixed pattern according to each of the signals of an engine speed by means of an ignition pulse PNe and of an idling detection by means of T Ho from a throttle SW, and operates an exhaust valve driving mechanism 1 by the aid of a motor 2. As the engine speed is increased, an exhaust valve is caused to open wider, while, in the case where the engine speed is gradually increased from the idling engine speed, when it is increased by more than a fixed rotational frequency from the idling engine speed, the exhaust valve is caused to operate once from its fully opened position to its fully closed position, and it is prevented that the valve will not function smooth ly owing to soots adhering to the valve.
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