To provide a compact engine capable of improving the start operability, while effecting sure start by enabling the shift to load running after start with a simple operation without needing operations of both a choke lever and throttle level in the start of the engine.

In a choke valve operating device of a rotary type throttle valvecarburetor 100 provided with a choke valve, a choke valve 17 can be operated manually in the start of an engine, while a start operating mechanism interlocked with the rotation of the throttle valve of the carburetor 100 to open automatically the choke valve 17 is disposed side by side with the carburetor 100.