KNOCK SENSOR MOUNTING STRUCTURE IN UNIT SWING ENGINE

To enable attachment/detachment work of a knock sensor to be facilitated and an intake system to be disposed at a low position in a unit swing engine in which: an intake pipe that stands upward from a cylinder head of an engine main unit, swingably supported by a frame body with a cylinder axis tilting forward, and extends rearward above the cylinder head and a cylinder block is connected to an upper wall of the cylinder head; and a knock sensor is fastened, with a screw member, to a mounting boss formed on an upper wall of the cylinder block. A mounting boss 51 is formed on an upper wall 26a of a cylinder block 26 at such a position as to avoid overlapping with an intake pipe 35 as seen in a direction along a screw axis SC of a screw member 53.