For example, in the idle speed and small load, the mixture must be very strong, the latter concentration gradually thinning; in the medium load, in order to fuel, and the fuel consumption rate of mixed gas carburetor supply minimum; under full load, in order to make the engine maximum power, to provide a rich mixture of carburetor. In addition, when a car starts cold, a stronger mixture is required. When accelerating, the carburetor is required to supply extra fuel when the throttle suddenly opens.

To sum up, the engine in normal working condition, the small, the load requirements of the carburetor with the increase of load can supply by thick gradually dilute gas mixture, under full load and the mixture composed of thin and thick, according to the above requirements, a simple carburetor only mentioned before is not satisfied. To meet these requirements, a series of gas concentration compensation devices are equipped on the carburetor. Such as the main pump, idling system, economizer, accelerating system and starting system, to ensure that the engine in different working conditions, the carburetor can mixed gas supply proper concentration.

Although the carburetor is not large, but the internal integration of so many systems, the structure becomes complex. Regular maintenance is very important to ensure that the carburetor can work regularly. The main disadvantage of using carburetor is distributing inflation and the mixture of the cylinder is not ideal, affect the engine performance and fuel economy improvement is very adverse to meet emission requirements, so it has been gradually replaced by EFI carburetor.