Two stroke combustion engine

The two-stroke combustion engine has a hollow piston that is movable in a cylinder (28). The inner space (4b) of piston serves as compressing space for air fuel mixture flowed into the cylinder during downward movement of piston. An outflow opening (21) for air fuel mixture, is provided in cladding of the piston. The outflow opening of piston is aligned with a bypass opening (20) provided in cylinder during upward movement of piston, so that air fuel mixture is allowed to pass through the bypass opening. An independent claim is included for method for operating the two-stroke combustion engine.