For operating an internal combustion engine with a combustion chamber delimited by a piston driving a crankshaft in a crankcase, with a device for supplying fuel, an ignition device, and an electronic control unit, wherein a correlation between a power output of the internal combustion engine and a lambda value in the combustion chamber is defined by a power output curve that has a first ascending branch, a maximum, and a second descending branch where the lambda value is smaller than 1, the position of an operating point of the internal combustion engine is determined by adjusting the ignition timing to an adjusted ignition timing and evaluating the engine speed reaction caused by the adjusted ignition timing. The supplied fuel quantity is changed as a function of the determined position of the operating point when the determined position of the operating point is not a desired operating point.