The carburetor is an important component in the motorcycle fuel supply system, located between the air filter and the engine air intake. Generally, motorcycle engines use flat suction in the direction of intake air flow, plunger type throttle valve, and float chamber type carburetor. The structure of the carburetor is mainly composed of two parts: the float chamber and the mixing chamber. The float chamber is located below the carburetor, and an oil pipe is connected to the fuel tank through the throttle switch. Through the needle valve on the float, the oil level in the float chamber is kept at a certain height, so that the oil supply pressure is stable. The function of the mixing chamber is to mix the vaporized and atomized gasoline with air, so that the engine can obtain the required mixture under various loads and speeds. It is composed of throttle valve, fuel injection needle, fuel injection pipe and gas and oil passages.
The rotation of the motorcycle throttle handle drives the throttle wire lanyard to control the up and down movement of the throttle valve and the fuel injection needle, changing the cross section of the intake throat and the fuel supply to meet the needs of the mixture under different speeds and loads. There is an idle speed adjustment screw on one side of the carburetor to adjust the idle speed. The idle stop screw is used to prevent the throttle from turning and to adjust the minimum throttle opening. There is a return spring above the throttle valve, which keeps the throttle valve closed when the throttle handle is not turned.
In some two-stroke motorcycle engines, in order to avoid the phenomenon of back injection in the carburetor at low speed, a one-way reed valve to control the intake air is installed between the carburetor and the cylinder block. The reed is made of thin spring steel, the valve seat is made of aluminum alloy, and there is an air inlet on it. . When inhaling, a certain degree of vacuum is formed in the crankcase. Under the action of the pressure difference, the reed valve opens the mixture and enters the crankcase. When the piston goes down and the ventilation port has not yet opened, the pressure in the crankcase rises, and the reed The valve is closed to prevent the reverse flow of the mixture, which improves the power and economy of the engine at low speed.