Abstract: A variable venturi-type carburetor comprising a suction piston which has a tip face. A raised wall is formed on the inner wall of the intake passage, which faces the tip face of the suction piston. The raised wall has a substantially straight extending tip edge. The inner wall of the intake passage and the tip edge of the raised wall define a D-shaped air inlet mouth. The connecting portions of the inner wall of the intake passage and the tip edge of the raised wall have an arc shape. The upstream end portion of the tip face of the suction piston and the tip edge of the raised wall define an isosceles triangular air inlet opening therebetween when the amount of air fed into the cylinder of the engine is small.

Abstract: A variable venturi-type carburetor comprising a vacuum chamber and an atmospheric pressure chamber which are separated by a suction piston. A needle is mounted on the central portion of the tip face of the suction piston. A suction hole, interconnecting the vacuum chamber to a venturi portion of the carburetor, is formed on the tip face of the suction piston at a position located upstream of the needle. The vacuum chamber is open to the atmosphere via a flow rate control valve apparatus when the engine temperature is low. The vacuum chamber is disconnected from the atmosphere by the flow rate control valve apparatus when the engine temperature is high.

Abstract: A variable venturi-type carburetor comprising a fuel passage which is open to an intake passage. An air bleed passage is connected to the fuel passage. The carburetor comprises an air bleed control valve device for controlling the flow area of the air bleed passage. The air bleed control valve device comprises a bore formed therein, a push rod slidably inserted into the bore for controlling the flow area of the air bleed passage, and a wax valve actuating the push rod. A cooling water passage is formed in the air bleed control valve device so as to surround the air bleed passage and the wax valve.

Abstract: A variable venturi-type carburetor comprising a suction piston which has a tip face defining a venturi portion. The tip face has a needle-mounting face at the center thereof, and a metering needle is fixed onto the needle-mounting face. The tip face also has a projecting tip face portion located upstream of the needle and projecting from the needle-mounting face towards the venturi portion. A groove, extending along the axis of the intake passage of the carburetor, is formed on the projecting tip face portion. The projecting tip face portion has a V-shaped cross-section which expands from the groove towards the venturi portion.

Abstract: A variable venturi-type carburetor comprising a suction piston which has a tip face defining a venturi portion. The tip face has a projecting tip face portion located upstream of the needle and projecting toward the venturi portion. A groove, extending along the axis of the intake passage of the carburetor, is formed on the projecting tip face portion. The projecting tip face portion has a V-shaped cross-section which expands from the groove toward the venturi portion. A projection, having a V-shaped cross-section, is formed on the inner wall of the intake passage, which faces the tip face of the intake passage, which faces the tip face of the suction piston. The projection enters into the V-shaped cross-section of the projecting tip face portion of the suction piston when the amount of air fed into the cylinder of the engine is small.

Abstract: Disclosed herein is a variable venturi carburetor including at least one pressure controlling port provided at the lower peripheral portion of the suction piston and adapted to face to a mixing chamber defined directly downstream of the venturi portion. The pressure controlling port is located at such a position as to communicate with the suction chamber and an atmospheric pressure chamber during middle and high intake air flowing stages as the suction piston reciprocates transversely with respect to the venturi portion, and to communicate with the suction chamber and the mixing chamber during low intake air flowing stage.

Abstract: A variable venturi-type carburetor comprising a suction piston, a fuel passage, and a needle fixed onto the suction piston and extending through the fuel passage. An air bleed passage is connected to the fuel passage. During engine starting, before the engine begins to rotate by its own power, the vacuum chamber of the suction piston is open to the atmosphere and the air bleed passage is shut off. When the engine begins to rotate by its own power, the vacuum chamber of the suction piston is closed from the atmosphere. After this, the air bleed passage is gradually opened. Such control of the closing of the vacuum chamber and the opening of the air bleed passage prevents engine stall by preventing the fuel mixture from becoming excessively lean when the engine first begins to rotate on its own power and then prevents engine misfires by subsequently reducing the air-fuel ratio to a lean mixture.