Fuel Injection (EFI)

Electronic fuel injection (EFI) does the same job as a carburettor – mixing fuel with air – but more precisely. A fuel pump supplies petrol under pressure to one or more injectors. The ECU opens each injector for a few milliseconds per cycle, based on sensor data, spraying finely atomised fuel into the intake port or throttle body.

A carburettor relies on airflow and vacuum to draw fuel in. EFI instead adjusts automatically for temperature, altitude and load, giving easier cold starts, better economy and lower emissions. EU emission rules mean nearly all new motorcycles, scooters and many off-road bikes are now injected; direct injection into the cylinder appears on some two-strokes.

Use fresh, clean fuel and change the fuel filter as specified. Symptoms such as hesitation, hard starting or a warning light often point to a sensor, connector or weak fuel pump; read fault codes before replacing parts.