Abstract: A silencer includes: a porous inner pipe provided in a peripheral wall thereof with a large number of small pores; an outer pipe surrounding the porous inner pipe; a sound absorbing material incorporated in an annular clearance between the porous inner pipe and the outer pipe; and a plurality of exhaust gas expansion chambers defined in the porous inner pipe and arranged such that an exhaust gas is sequentially passed through the exhaust gas expansion chambers. The sound absorbing material is formed of a heat-resistant fiber layer which is wound around an outer peripheral surface of the porous inner pipe with a binder interposed therebetween, and an outer peripheral surface of the heat-resistant fiber layer is press-fitted to an inner peripheral surface of the outer pipe with a predetermined interference. Thus, it is possible to prevent a reduction in sound vanish effect due to the leakage and short-circuiting of an exhaust gas and a reduction in engine power performance.

Abstract: A body frame for a motorcycle including a head pipe for supporting a rotary shaft for a handle, a pair of left and right main body frame elements, connected to the head pipe and extending rearwardly of the head pipe, a pair of left and right engine supporting members, connected to and extending downwardly from the main body frame elements adjacent to said head pipe, and a horizontally extending frame element connecting said left and right main body frame elements to each other at intermediate portions in the longitudinal direction. The engine is supported at least at a lower end portion of the left and right engine supporting members and intermediate portions in the longitudinal direction of the left and right main body frame elements and an upper end portion of a shock absorber is connected to the horizontally extending frame elements.

Abstract: A casting mold is provided for a body frame for a motorcycle including a head pipe for supporting a rotary shaft for a handle, a pair of left and right main body frame elements, connected to the head pipe and extending rearwardly of a car body, a pair of left and right engine supporting members, connected to and extending downwardly from the main body frame elements adjacent to said head pipe, and a horizontally extending frame element connecting said left and right main body frame elements to each other at intermediate portions in the longitudinal direction. The engine is supported at least at a lower end portion of the left and right engine supporting members and intermediate portions in the longitudinal direction of the left and right main body frame elements and an upper end portion of a shock absorber is connected to the horizontally extending frame elements.