Abstract: An exhaust muffler for an internal combustion engine included in a motorcycle includes a perforated inner pipe (32), an outer pipe (31) coaxially surrounding the inner pipe (32), and a glass wool mat (33) packed in a space between the inner pipe (32) and the outer pipe (31). A three-layer protective structure is formed by winding an inner stainless steel wire mesh (34) wound around the inner pipe (32), winding a stainless steel wool mat (35) around the inner stainless steel wire mesh (934), and winding an outer stainless steel wire mesh (36) around the stainless steel wool mat (35). The glass wool mat (33) is wound around the three-layer structure. The three-layer structure extends the life of the glass wool mat (33) even if the temperature and pressure of the exhaust gas discharged by the internal combustion engine increase.

Abstract: An exhaust control valve has a valve housing and a valve body rotatably contained within the valve housing. The valve body cooperates with the valve housing for controlling the flow of exhaust gas. A transmission member rotationally drives a valve shaft of the valve body. The valve body is formed in a cylindrical shape and coaxially with an axis line of the valve shaft. The valve body and the valve shaft are made from a one-piece body by casting. This arrangement provides an exhaust control valve for an engine having a valve body that provides excellent sealing properties, demonstrates high response to driving torque and is easy to manufacture through casting.

Abstract: In an exhaust control valve having a valve housing and a valve body rotatably contained in the valve housing, a transmission member is fitted to an outer end of the valve shaft and protrudes from the outside of the valve housing. A bearing bushing for rotatably bearing an external circumferential surface of the valve shaft by its internal circumferential surface and rotatably bearing an end face of the valve body by its end face is mounted in the valve housing. The valve body is urged by load from a thrust spring for achieving a pressure contact seal condition between the opposed end faces of the bearing bush and the valve body.

Abstract: A partitioning member for dividing a connecting pipe into at least two exhaust passageways is provided in the connecting pipe, which is attached to an exhaust side of a silencer. A valve mechanism is operable to vary the passageway area of one of the exhaust passageways. With this structure, for example, when an engine is rotating at low revs, exhaust gas is discharged from the exhaust passageway without the valve mechanism, while when the engine is rotating at high revs exhaust gas is simultaneously discharged from the exhaust passageway having no valve mechanism and a passageway provided with the valve mechanism. Therefore, it is possible to reduce exhaust noise when the engine is rotating at low revs.

Abstract: An exhaust muffler for an internal combustion engine included in a motorcycle includes a perforated inner pipe (32), an outer pipe (31) coaxially surrounding the inner pipe (32), and a glass wool mat (33) packed in a space between the inner pipe (32) and the outer pipe (31). A three-layer protective structure is formed by winding an inner stainless steel wire mesh (34) wound around the inner pipe (32), winding a stainless steel wool mat (35) around the inner stainless steel wire mesh (934), and winding an outer stainless steel wire mesh (36) around the stainless steel wool mat (35). The glass wool mat (33) is wound around the three-layer structure. The three-layer structure extends the life of the glass wool mat (33) even if the temperature and pressure of the exhaust gas discharged by the internal combustion engine increase.

Abstract: A partitioning member for dividing a connecting pipe into at least two exhaust passageways is provided in the connecting pipe, which is attached to an exhaust side of a silencer. A valve mechanism is operable to vary the passageway area of one of the exhaust passageways. With this structure, for example, when an engine is rotating at low revs, exhaust gas is discharged from the exhaust passageway without the valve mechanism, while when the engine is rotating at high revs exhaust gas is simultaneously discharged from the exhaust passageway having no valve mechanism and a passageway provided with the valve mechanism. Therefore, it is possible to reduce exhaust noise when the engine is rotating at low revs.

Abstract: A partitioning member for dividing a connecting pipe into at least two exhaust passageways is provided in the connecting pipe, which is attached to an exhaust side of a silencer. A valve mechanism is operable to vary the passageway area of one of the exhaust passageways. With this structure, for example, when an engine is rotating at low revs, exhaust gas is discharged from the exhaust passageway without the valve mechanism, while when the engine is rotating at high revs exhaust gas is simultaneously discharged from the exhaust passageway having no valve mechanism and a passageway provided with the valve mechanism. Therefore, it is possible to reduce exhaust noise when the engine is rotating at low revs.

Abstract: In an exhaust control valve having a valve housing and a valve body rotatably contained in the valve housing, a transmission member is fitted to an outer end of the valve shaft and protrudes from the outside of the valve housing. A bearing bushing for rotatably bearing an external circumferential surface of the valve shaft by its internal circumferential surface and rotatably bearing an end face of the valve body by its end face is mounted in the valve housing. The valve body is urged by load from a thrust spring for achieving a pressure contact seal condition between the opposed end faces of the bearing bush and the valve body.

Abstract: An exhaust control valve has a valve housing and a valve body rotatably contained within the valve housing. The valve body cooperates with the valve housing for controlling the flow of exhaust gas. A transmission member rotationally drives a valve shaft of the valve body. The valve body is formed in a cylindrical shape and coaxially with an axis line of the valve shaft. The valve body and the valve shaft are made from a one-piece body by casting. This arrangement provides an exhaust control valve for an engine having a valve body that provides excellent sealing properties, demonstrates high response to driving torque and is easy to manufacture through casting.

Abstract: To effectively reduce noise caused by an attachment part of a cam chain guide without increasing a pressing force of a cam chain tensioner more than is necessary. A cam chain guide for slidably guiding a cam chain at a valve gear of a four cycle engine is made of resin. An attachment hole for an attachment bolt is provided at an attachment end section for the crankcase. Side surface projections are provided equally spaced at the periphery of an attachment surface surrounding the attachment hole so as to project from a normal surface. Annular recesses are formed at the peripheries of each of the side surface projections. Furthermore, inner surface projections are provided at the inner peripheral surface of the attachment hole equally spaced about the periphery so as to project in a central direction.