PURPOSE: To shorten the length of an intake path from a carbureter to an intake port to improve response property by devising an intake port forming portion in the heading engine and arranging an air duct and an air cleaner at the rear side of the carbureter.

CONSTITUTION: A partition plate 23 having an intake port 22 is arranged at one longitudinal end side of a crankshaft 18 of a 2-cycle engine, i.e. at the side of a crank chamber 21 at the left side, and in a thin space between the partition plate 23 and a valve cover 3 is disposed rotatably a rotary valve 25. The valve cover 3 is provided with an intake path 24 which extends back upward along the direction of connecting the rotary valve 25 and an inlet 3a of said path 24 is formed with an opening tapered backward. And a cylindrical outlet 4b of a carbureter 4 fits the inlet 3a through an annular rubber holder 38 and an air cleaner 6 is connected to the back of the carbureter 4 through a duct 5.