carburettor

A carburettor is a device in internal combustion engines that blends air and fuel for combustion. In a conventional gasoline engine, air enters through the intake and passes through a venturi, a narrowing that creates a drop in pressure and draws fuel from a float chamber through a metering jet. The resulting air–fuel mixture is delivered to the intake manifold and then to the cylinders for ignition.

The float chamber maintains a steady fuel level by means of a float and needle valve connected to the fuel supply. As fuel is consumed, the float valve opens to replenish the bowl. The choke is used to enrich the mixture for cold starting by restricting air flow. Carburettors typically include several circuits to meter fuel at different throttle positions: idle, main, and sometimes intermediate or transition circuits, each with jets and needles corresponding to fuel needs at various engine speeds. Some designs include an accelerator pump or enrichment mechanism to provide a temporary rich mixture during rapid throttle opening.

Compared with electronic fuel injection, carburettors rely on air flow to meter fuel and are generally less precise in controlling mixture, particularly under changing altitude and temperature. They require regular maintenance, including cleaning of jets and gaskets and adjustment of needles. Carburettors remain common in many small engines, motorcycles, and older vehicles, while modern cars predominantly use fuel injection for improved efficiency and emissions control.