To properly control a scavenging air/fuel-air mixture in a stratified scavenging two-cycle engine with a crankcase compression scavenging system by using an optional carburetor.

A driving member 32A which is turned by an accelerator operation is installed on the air valve 15A of an air passage 14 to enable an angular reciprocation. Further, a driven member 37A which always contacts the cam 35A provided on the driving member 32A is installed at the throttle valve 22A of a carburetor 18A to enable a linear reciprocation interlocking with a fuel flow control mechanism 61. Consequently, the carburetor 18A can freely be designed irrespective of the air passage 14, and also the opening degree relation of the air valve 15A with the throttle valve 22A is properly maintained by an interlocking mechanism 31A in which the cam 35A and spring 44A are used and causes no looseness or play. Therefore, the engine can safely be operated without deranging an air/fuel ratio.