PURPOSE: To prevent supply of fuel from decreasing when a Venturi is opened to a high degree, by supplying bleed air of pressure, in which a pressure in a Venturi part is added in addition to the atmospheric pressure, to a secondary main nozzle in a variable Venturi carburetor.
CONSTITUTION: In the case of a carburetor, which constitutes a variable Venturi actuated by turning an air quantity control valve 2 provided in the upstream of a throttle valve 19, a secondary main nozzle 6, for use when the Venturi is opened to a large degree, is provided in the upstream of a primary main nozzle 5. Bleed air from an atmospheric air bleed introducing hole 7 and from an auxiliary air bleed 28, introducing a pressure in a Venturi part, is supplied to the secondary main nozzle 6. The carburetor, in which a large negative pressure acts in the auxiliary air bleed 28 when the Venturi comes to be opened in a large degree especially in a half stage to the high degree opening, decreases a bleed quantity of the atmospheric air to supply a rich mixture.
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