To facilitate the control of the working and assembling accuracy of the mixture jet and jet needle of a carburetor by integrating its fuel systems into one simple system, stably supplying fuel at a proper air-fuel ratio, and under a smaller opening degree of its sliding throttle valve reducing a fluctuation in the intake air flow to the lift level, of the sliding throttle valve as well as reducing the intake negative pressure acting on its fuel injection port.
A pressure-controlled chamber 24 controlled under a negative pressure as not causing air compression mixes air and fuel together to obtain a mixture of a fixed air-fuel ratio which is then mixed with air metered in a sliding throttle valve 5. When the sliding throttle valve 5 is opened only by a predetermined opening degree or below, only a main intake throttle port 10 formed at the lower part of a side wall 6a of the throttle valve 5 on the intake upstream side controls the opening area of an intake passage 3 as well as an auxiliary throttle port 11 formed on the downward side to a fuel injection port 21 reduces the intake negative pressure acting on the fuel injection port, to thereby prevent the mixture flow from being sensitively affected by the accuracy of a mixture jet 22 and a jet needle 31.
MINOURA MIKIO
SUZUKI SATORU
SATO SHINJI
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