Abstract: Hollow closed-sectional elongate member is provided by bending a plastic strip widthwise. The closed-sectional elongate member has a crimped joint section provided on any one of its walls. The crimped joint section is formed by crimping together opposite longitudinal edge portions of the strip as the strip is bent widthwise. The crimped joint section extends along the length of the closed-sectional elongate member and thus functions as a rib reinforcing the rigidity of the elongate member. The closed-sectional elongate member is also curved along its longitudinal direction, to provide a closed-sectional curved elongate member.

Abstract: A first mandrel segment comprised of first and second resinous sheets including proximal end portions vertically spaced from each other is initially inserted into a pipe having a weld seam extending longitudinally thereof. Since the first mandrel segment has a thickness smaller than an inside measurement of the pipe, the first mandrel segment can be inserted into the pipe without being caught by a bulged portion of the weld seam protruding inwardly of the pipe. After the insertion of the first mandrel segment, a second mandrel segment comprised of a third resinous sheet is forced into a spacing between the first and second resinous sheets. By thus forcing the third resinous sheet into the spacing, the first resinous sheet is pushed vertically to come into intimate contact with the bulged portion. The pipe having the first, second, and third resinous sheets thus inserted therewithin is then bent by a bender. After the bending of the pipe, the third resinous sheet is first pulled out of the bent pipe.

Abstract: In a motorcycle power unit, a crank shaft (56) and a clutch shaft (57) disposed on the right side (in the figure) from a body center (127) and a cylinder head (129H) is disposed on the left side from the body center (127). Since the crank shaft, the clutch shaft and a transmission shaft are disposed on one of right and left sides with respect to the body center and the cylinder is disposed on the other side with respect to the body center, it becomes possible to make a favorable lateral balance of the power unit.