Abstract: An engine unit includes a cylinder block of a short-skirt type which has a plurality of first partition walls and a plurality of crank journals formed on the partition walls and rotatably receiving the crankshaft. Bearing caps are fitted to the crank journals and rotatably hold the crankshaft in cooperation with the crank journals. A lower case is fixed to the cylinder block and covers the crankshaft. The lower case includes a pair of flanges abutting against the lower edges of the skirt portions, a semi-cylindrical bottom wall, and a plurality of second partition walls formed on the bottom wall to oppose the first partition walls. Each bearing cap is clamped between the first and second partition walls. The lower case is fixed to the cylinder block by means of first bolts screwed into the skirt portions through the flanges, and second bolts screwed into the crank journals through the second partition walls and bearing caps.

Abstract: A belt tensioner comprising an intermediate annular member rotatably provided around a fixed member in the form of a solid cylinder and to be secured to a stationary portion, a movable eccentric member in the form of a solid cylinder and rotatably provided around the intermediate annular member eccentrically therewith, an idler in the form of a hollow cylinder and rotatably provided around the movable eccentric member for contact with a belt, and a spring provided between the stationary portion or the fixed member and the movable eccentric member for biasing the movable eccentric member in a direction to bring the idler into pressing contact with the belt. The intermediate annular member has a cylindrical or tapered first sliding surface in contact with the fixed member and a cylindrical or tapered second sliding surface in contact with the eccentric member.