| 摘要 |
PURPOSE:To prevent overrichment of a fuel mixture in warming-up of an engine with a choke valve closed, by providing a temperature sensing valve and an operating valve adapted to be opened and closed under respective specific conditions, in a vacuum passage for transmitting a suction vacuum to a power device for increasing a fuel supply quantity. CONSTITUTION:When engine temperature is not greater than a predetermined value, a first branch passage 19 is closed by a temperature sensing valve 21. Then, a choke valve 27 is closed by a manual choke opening/closing mechanism 24, and an engine is started to carry out warm-up operation. At this time, a detection switch 29 is turned on in association with retraction of a choke knob 25, so that a solenoid coil of an operating valve 22 is excited to retract a valve member 22a of the operating valve 22 and thereby make a second branch passage 20 communicated. Therefore, engine warming-up vacuum is admitted into a cylinder chamber 13 of a power device 9 to thereby lift a power valve 10 through a power piston 12 and close a power jet 8. Accordingly, fuel supply from the power jet 8 is cut to prevent overrichment of a fuel mixture.
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