Working Principle of Carburettor : All carburettors work on one basic principle, the venturi. A venturi is a very simple device that changes air pressure by changing the velocity of the air. As velocity increases, pressure drops and as velocity decreases, pressure rises. As air travels through the narrow part of the venturi, its velocity increases and the pressure drops. If there is a fuel passage at that low pressure point and the fuel reservoir is at a higher pressure, fuel will be pushed into the venturi, i.e. a carburettor needs a pressure difference to allow flow of fuel. Venturi, thus, creates the pressure difference.
We will discuss working of piston type carburettor at various operating conditions that is used in Hero Honda motorcycles.