INTERNAL COMBUSTION ENGINE FOR MOTORCYCLE

An internal combustion engine for a motorcycle provided with a leg shield (15) having right and left side walls extending on the opposite sides of a front frame (2) extending obliquely downward toward the rear from an upper part of a front fork (5). The internal combustion engine includes a cylinder (10) and a cylinder head (11). The internal combustion engine is suspended from the front frame (2) with the axis (C) of the cylinder (10) substantially horizontally extended, and the right and the left side wall of the leg shield (15) are extended on the right and the left side of the front frame (2), respectively, so as to cover the opposite sides of the cylinder (10) and the cylinder head (11). At least either the cylinder (10) or the cylinder head (11) is provided on its upper and lower side surfaces with first cooling fins (10a, 11a) parallel to the axis (C) of the cylinder (10), and at least either the cylinder (10) or the cylinder head (11) is provided on its right and left side surfaces with second cooling fins (10b, 11b) extending perpendicularly or substantially perpendicularly to the axis (C) of the cylinder (10). The substantially vertical second cooling fins (10b, 11b) enable air that has flowed into the depth of a space defined by the internal combustion engine (8), the front frame (2) and the right and the left side wall of the leg shield (15) to flow downward.