A two-cycle engine having a piston reciprocalbly mounted in a cylinder in which a combustion chamber is formed. In prescribed positions of the piston, the combustion chamber communicates with a crankcase via at least one transfer channel. A portion of an intake channel for supplying fuel/air mixture and combustion air is formed in a carburetor, in which is pivotably mounted a butterfly valve for controlling the flow cross-section of the intake channel. A fuel opening opens into the intake channel portion, and downstream of the carburetor the intake channel is divided into a mixture channel andan air channel. A mechanism is disposed on the butterfly valve to increase the speed of flow in the carburetor in the vicinity of the fuel opening.