A diaphragm carburetor is provided for an internal combustion engine that operates with scavenging air, especially a two-cycle engine in a manually-guided implement. The carburetor has an intake channel portion in which is disposed a butterfly valve that is rotatably held via a shaft and in the vicinity of which fuel-supplying channels open into the intake channel portion. The channels are supplied from a fuel-filled regulating chamber that is formed on a longitudinal side of the intake channel portion in the carburetor housing and is separated by a regulating diaphragm from a compensation chamber. The carburetor has at least one air channel that supplies additional combustion air and that has an air valve that is rotatably held via a shaft. The butterfly valve and the air valve can be brought from a closed position, in which the butterfly valve or the air valve only insignificantly influence the flow in the intake channel portion or in the air channel, into a closed position in which the intake channel portion or the air channel are substantially closed off in an airtight manner, and in an opening direction from the closed position into the opened position. The air valve is coupled to the butterfly valve via a coupling mechanism that compensates for axial and radial tolerances and includes a spring.