| 摘要 |
PROBLEM TO BE SOLVED: To change the air-fuel mixture gas concentration characteristic in a low open zone of a sliding throttle valve by opening an engine side semi- annular air passage or an air cleaner side semi-annular air passage of an annular air passage opened to an intake passage in a sliding throttle valve-type carbureter. SOLUTION: When an internal combustion engine is operated, and the negative pressure produced in an intake passage 2 acts on an opening of a main nozzle 20, the fuel in a float chamber 6 is discharged into the intake passage 2 through a gap between a jet needle 4 and the main nozzle 20. This fuel is mixed with the air discharged into the intake passage 2 from an engine side semi-annular air passage 7B by closing an air cleaner side semi-annular air passage 7A by a semi-annular collar 20A formed on an upper outer periphery of the main nozzle 20. The concentration of the air-fuel gas can be comparatively thinned over the whole range of the intake negative pressure by releasing only the semi-annular air passage 7B, whereby the characteristic of the change of the air-fuel mixture gas concentration can be properly changed.
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