Carburetor is commonly known as carburetor. The most important equipment in gasoline engine fuel supply system. To vaporize gasoline and form an even mixture with air. It is usually composed of float, float chamber, needle valve, pipe, jet pipe and metering hole. Gasoline pumped from the inlet into the float chamber, which has a needle valve connected to the float, to control the oil level to maintain a certain level of oil. Gasoline from the float chamber through the orifice into the jet pipe. The oil level of the injection pipe outlet is about 3 ~ 5mm higher than that of the float chamber, which can prevent the oil spill. As the piston moves down and the inlet valve opens, air from the air filter enters the inlet and flows through the choke valve into the carburetor. When the air flows through the pipe, it becomes negative pressure due to the sudden increase of the flow rate. Under the action of pressure difference, gasoline shoots out of the pipeline and is blown into countless tiny oil droplets by the high-speed air. The oil mist evaporates and mixes with air along the way, forming a uniform combustible mixture that then enters the cylinder. The amount of gasoline ejected by the fuel injection pipe is determined by the diameter of the orifice, while the amount of combustible mixture entering the cylinder is controlled by the throttle valve (commonly known as "accelerator"). According to the direction of air flow, there are two types: upper suction type and lower suction type. According to different structure, there are single - jet pipeline carburetor and multi - jet carburetor. A simple carburetor can only meet the needs of a small petrol engine with a very stable load. For most of the gasoline engine working load change often, have to adopt a starting, idle (idle), add thick the carburetor, acceleration and a series of auxiliary equipment, can according to the requirements of all kinds of different working conditions, load change and automatically change the concentration of the combustible mixture, to ensure the good performance of the engine and lower fuel consumption rate.