PURPOSE: To make an overhang compact in constitution by arranging a carburetor and a governing mechanism in such a way as to be adjacent up and down with respect to a suction manifold overhung to the outside of an engine block.

CONSTITUTION: In a multi-cylinder straight engine where its crank shaft T extends horizontally and the center line of its cylinder extends roughly vertically, a gear case 2 is mounted on one end surface of an engine block 1, and furthermore a suction manifold 3 is mounted on one upper side surface of the engine block 1. And a carburetor 6 is arranged in a place adjacent to said suction manifold 3 wherein a throttle valve is connected with the lever 7 of the carburetor 6 provided on the end section opposite to the gear case 2. The gear case 2 is overhung to the outside of the engine block 1 and the governor case 20 of a governor 11 is mounted on the end surface at the engine block (1) side of said overhang section 8 wherein said case 20 is overhung downward with respect to the suction manifold 3.