Abstract: An airstream driven rotor assembly with a centrifugal pump forcing a measured fuel quantity through a fixed orifice in direct substantially linear proportion to rotor speed and thus to airstream volume. The ultimate fuel-air ratio is corrected for optimum operation by slightly changing, in response to measured parameters, one of the mixture constituents. In one embodiment, the fuel discharge bore (9) of a rotor (7) is dimensioned that the rotor carburetor (2) produces a lean mixture with a .lambda.-value which is constant for all operating points approximately 1.25. For fuel-air ratio correction additional fuel is brought into atomization ring (11) of rotor (7), by which the fuel-air ratio in the lean mixture is changed and at the engine operating points the .lambda.-values are adjusted to give most favorable fuel consumption, output and pollution.