The carburetor is an important part of the motorcycle fuel supply system, located between the air filter and the engine air intake. Generally, motorcycle engines use flat suction, the throttle valve is plunger, and the float chamber carburetor. The structure of the carburetor is mainly composed of two parts: a float chamber and a mixing chamber. The float chamber is located below the carburetor, and there is an oil pipe passing through the fuel tank through the throttle switch, and the needle valve on the float keeps the oil level in the float chamber at a certain height, so that the fuel supply pressure is stable. The function of the mixing chamber is to mix gasoline vaporized and atomized with air, so that the engine can obtain the required mixture under various loads and speeds. It is composed of a festival valve, a fuel injection needle, a fuel injection pipe, gas, and oil passages.
The rotation of the motorcycle's throttle handle drives the throttle wire lanyard to move the throttle valve and the fuel injection needle up and down to change the intake throat section and fuel supply to meet the needs of mixed gas under different speeds and loads. An idle speed adjustment screw is installed on one side of the carburetor to adjust the idle speed. The idle stop screw is used to prevent the rotation of the throttle valve and adjust the minimum opening of the throttle valve. There is a return spring above the throttle valve to keep the throttle valve closed when the throttle handle does not rotate.
In some two-stroke motorcycle engines, in order to avoid the back-injection phenomenon of the carburetor at low speed, a one-way reed valve that controls the intake of 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 the air inlet is opened on the upper part. The air inlet plane and the contact part of the reed are pasted with a layer of oil rubber to reduce the impact and vibration of the reed and the valve seat. . When the air is inhaled, a certain degree of vacuum is formed in the crankcase. Under the action of the pressure difference, the reed valve opens the mixed gas and enters the crankcase. When the piston descends and the air exchange port has not yet opened, the pressure in the crankcase rises and the reed The valve is closed to prevent the mixed gas from flowing backward, which improves the power and economy of the engine at low speed.