Method for adjusting the air-fuel ratio of an internal combustion engine, in a fuel supply section thereof, such as a carburettor or a fuel-injection system, the fuel supply section having a control unit for adjusting the air-fuel ratio of the engine, and the engine having an engine speed and an engine throttle ranging from zero throttle to full throttle. The method including: a) measuring the engine speed of the engine; b) comparing the engine speed to a first engine speed value; c) adjusting the air fuel ratio if the engine speed is lower than the first engine speed value; and d) repeating a) to c) until the engine speed is either greater than or equal to the first engine speed value.