Working principle of the carburetor

The carburetor is actually a tube called the throttle board to control the air flow through the tube. There is a contracted part of the tube called the venturi tube, in which a vacuum forms. This shrinkage part has a volume hole, from which the fuel is inhaled by vacuum.


Motorcycle carburetor looks very complicated, but just by mastering some principles, you can adjust the motorcycle to the best condition. All the carburetors operate under the basic principles of atmospheric pressure. Atmospheric pressure is a powerful force that puts pressure on everything. It can vary slightly, but usually has 15 pounds of pressure (PSI) per square inch. This means that atmospheric pressure is fifteen pounds per square inch for anything. By changing the atmospheric pressure in the engine and carburetor, it is possible to change the pressure and make the fuel and air flow through the carburetor.


Atmospheric pressure spreads from high pressure to low pressure. When the piston of the two-stroke engine is at the upper stop (or the piston of the four-stroke engine), a low pressure forms under the piston in the crankcase (above the piston of the four-stroke engine). This low pressure can also cause a low pressure in the carburetor. Because of the pressure outside the engine and carburetor is high, the air will rush into the carburetor and enter the engine until the pressure is balanced. The air flowing through the carburetor will drive the fuel, which will then be mixed with the air.


Inside the carburetor is a tube of the throat. The throat is a shrinking part inside the carburetor that forces the air to accelerate through. A suddenly narrowed river is used to illustrate what happens in the carburetor. The river accelerates near the narrowed banks, and even faster if the banks narrow continuously. If the same thing happens in the carburetor, the accelerated flow of air will cause the pressure inside the carburetor to drop.


Gasoline is from the fuel tank through the gasoline filter into the carburetor, the gasoline filter can filter out the impurities mixed with the gasoline and the oxide skin in the fuel tank. If the quality of the filter is defective, some impurities still pass through the filter. In addition, gasoline contains components that can form colloid, which will condense colloid after long time deposition and be attached to the parts of the carburetor (such as measuring hole), the oil channel and the surface of the float chamber.


The air enters the carburetor through the air filter. Based on the intake resistance not being too large and other factors, the filter device should not be too dense, so some small impurities in the air will still enter the carburetor through the air filter. If the quality of the filter is defective, it will cause more serious effects.


More components in the carburetor duct, airway, such as main volume hole, idle volume hole, main air volume hole, main foam tube and so on have a small inner diameter (inner diameter between 0.3~1.5mm), into the gasoline impurities, colloid and impurities in the air in the carburetor, often change or blocked, lead to the carburetor airway, oil channel, make the oil supply characteristics of the carburetor change, and even cause the failure of carburetor performance.

Working principle of the carburetor