Motorcycle carburetors work by mixing the right amount of gasoline with air so that the engine runs properly. Most carburetors used on motorcycles also use a throttle plate to regulate the airflow inside the motorcycle's engine.
The carburetor, or venturi, contains an intake manifold that regulates the ratio of air and fuel in the engine. When the piston moves down the intake manifold, it creates a vacuum that causes an increase in pressure in the chamber of the carburetor. The pressure forces the fuel-air mixture through the fuel-air outlet passage, or ports, in the carburetor and is vaporized by the fast moving air stream. Motorcycles also use a throttle valve connected to the throttle cable to regulate the airflow in the carburetor. Some expensive aftermarket carburetors have additional circuits and ports for fuel to enter the air, as well as an idle circuit that is used to fine-tune the fuel mixture. A fuel pump stored in the fuel bowl is used to deliver gasoline to the carburetor. The level of fuel in the bowl is kept constant under all conditions using a float system that lowers and opens the valves to let more fuel in when the fuel level drops below a certain level.