The air cooled engine is constructed with a cooling fan (29), driven in rotation by the engine (5), to direct cooling air from the vicinity of the crankshaft (9) towards the cylinder (20) and cylinder head (21). Cooling fins (26 and 27) are spaced axially along the length of the cylinder and parallel to the line of the cylinder around the cylinder head. Streamlining (24) and a cover (23) are arranged to direct the air flow over the cooling fins. The spacing between the edge of the cooling fins along the cylinder and the streamlining is greater closer to the fan and the spacing between the streamlining and the edges of the fins on the cylinder head is greater in the vicinity of the air outlet (37) and closer to the fan. |