In carburetor, the fuel is completely broken into the minute particles, vaporized and mixed with the air in a proper ratio. The homogeneous mixture of fuel and air thus obtained is supplied to the engine cylinder during the suction stroke of engine.
The main purpose of carburetoris to supply the required quantity of petroland air mixture, of the correct strength as per requirement of load conditions of the engine. The ratio should not be more than 20:1 and not less than 8:1. The ideal ratio is 15:1
How does a carburetor work?
A carburetor relies on the vacuum created by the engine to draw air and fuel into the cylinders.The throttle can open and close, allowing either more or less air to enter the engine. This air moves through a narrow opening called a venturi. The vacuum is a result of the airflow required to keep the engine running.
To get an idea of how a venturi works, picture a river flowing normally. This river is moving at a steady pace and the depth is very consistent for the entire length. If there is a narrow section in this river, the water will have to speed up for the same volume to get through at the same depth. Once the river returns to the original width after the bottleneck, the water will still try to retain that same velocity. This makes the higher-velocity water on the far side of the bottleneck pull on the water approaching the bottleneck, creating a vacuum.
Thanks to the venturi, there is enough of a vacuum inside of a carburetor for the air passing through it to steadily draw gas from the jet. Found inside of the venturi, the jet is an opening where fuel from thefloat chamber can mix with air before entering the cylinders. The float chamber holds a small amount of fuel, like a reservoir, and allows fuel to easily flow to the jet as it is needed. As the throttle opens, more air is drawn into the engine, bringing with it more fuel, which makes the engine create more power.
The main issue with this design is the fact that the throttle has to be open for the engine to get fuel. The throttle is closed at idle, so an idle jet allows a small amount of fuel to enter the cylinders to keep the engine from stalling. Other small issues include excess fuel vapor escaping the float chamber(s).