Abstract: A power unit provided with a dry sump type lubricating device includes a power unit case that is covered in part by a power unit case cover and is divided into a front unit case and a rear unit case. The power unit also includes a crankshaft rotatably supported by a crank chamber that is formed by the power unit case and a shift shaft rotatably supported by a transmission chamber that is provided adjacent to the crank chamber. The power unit also includes an oil tank disposed on the crank chamber side of an anteroposterior outside surface of the power unit case cover and a hydraulic control device for controlling a shift clutch, disposed on the transmission chamber side of the anteroposterior outside surface of the power unit case cover.

Abstract: A transmission assembly includes a shift drum operable to rotate in first and second directions. The shift drum includes a common speed change position, where both a fastest forward gear and a reverse gear are capable of becoming engaged, in such a manner that a reverse stopper arm fits at a first end of a reverse cam groove formed on the shift drum. When the shift drum is rotated in the second rotation direction, opposite to the first direction, from a state where the reverse gear is engaged, the reverse stopper arm surmounts the outer periphery of the shift drum from the first end of the reverse cam groove, without requiring the application of an external force thereto, so as to become detached and to move towards a second end of the reverse cam groove.

Abstract: A vehicular transmission includes a shift drum center with a plurality of gear train establishment notches disposed, equally spaced apart from each other, on the outer periphery thereof. The gear train establishment notches establish a specific gear train selected from among a plurality of gear trains by selectively engaging a drum stopper arm therein. The shift drum center further includes half neutral notches to be engaged with the drum stopper arm. The half neutral notches are disposed on the outer periphery of the shift drum center and at a central portion between each pair of the gear train establishment notches, respectively. The resulting configuration effectively suppresses an engagement noise during changing of a gear position through a sliding motion of a shifter.

Abstract: To reduce the engaging sound to a low level, generated at the time of changing over the change gear stage by sliding a shifter, an intermittent feed mechanism includes a drum shifter, a pair of pawls symmetrically mounted to the drum shifter and energized in tilting-up directions, engaging recesses provided at regular intervals along the circumferential direction at the inner periphery of a shift drum center so as to be capable of engagement with both the pawls, and a fixed guide plate for guiding the tilted conditions of both the pawls. The guide plate is provided with a large-diameter arcuate part, a small-diameter arcuate part, and connecting parts. The pawls are engaged with the engaging recesses by the connecting parts, in the course of turning of the drum shifter by a turning amount necessary for changing over the establishment conditions of a plurality of change gear stages of gear trains.

Abstract: A vehicular transmission for an internal combustion engine includes lead grooves disposed on an outer periphery of a shift drum having communication portions connecting a pair of gear train establishment portions extending circumferentially along the shift drum. The communication portions include half neutral portions formed at a center thereof, extending circumferentially along the shift drum. The resulting configuration suppresses an engagement noise to a minimum during changing of a gear position through a sliding motion of a shifter.

Abstract: A power unit for a vehicle includes a buffering device provided on a final shaft parallel to a countershaft of a speed change gear which is configured to change a speed resulting from rotational power inputted from an engine stepwise. The buffering device includes a damper gear wheel supported for relative rotation on the final shaft, a lifter coupled against relative rotation but for relative movement in an axial direction on the final shaft and engaged by a cam provided on one face of the damper gear wheel, a spring retainer supported at a position on the final shaft spaced apart from the lifter, and a coil spring provided between the lifter and the spring retainer in such a manner as to exert spring force for biasing the lifter toward the damper gear wheel.

Abstract: An internal combustion engine includes: an engine body including: a crankcase for rotatably supporting a crankshaft; and a crankcase cover fastened to the crankcase by a plurality of bolts so as to cover one side of the crankcase; and a stay supporting an oil level gauge guide, the stay being mounted on the engine body, the stay having an opening receiving and supporting a tube or wire.

Abstract: A vehicle transmission includes first and second main shafts that enable switching of power transmission from an engine; a counter shaft connected to a drive wheel; and gear trains with a plurality of shift stages provided between each of the first and second main shafts and the counter shaft. The vehicle transmission also includes shifters which switch between engagement with and disengagement from a gear constituting part of each of the gear trains so as to switch the established states of the gear trains, and to prevent, during running at the most frequently used shift stage, the occurrence of gear rattle produced by a gear train other than the gear train with such a shift stage. With this configuration, in the running state of using a particular gear train with the highest frequency of the established states among the gear trains, the gear trains, excluding the particular gear train, are in the non-established state.

Abstract: A starting clutch includes a clutch inner that is secured to and supported by a drive plate boss fitted to a crankshaft near the end thereof. A one-way clutch is fitted to the outer periphery of the cylindrical portion extending inwardly. A clutch outer forms an annular portion that covers the outer periphery of the drive plate. A hollow disk portion covers the inner surface and is rotatably supported by the crankshaft. The one-way clutch is clamped by the inner peripheral edge of the hollow disk portion of the clutch outer from the outer peripheral side in cooperation with the cylindrical portion of the drive plate boss, and the inner peripheral edge of the hollow disk portion of the clutch outer abuts against a flange portion of the drive plate boss extending along the inner surface of the drive plate in the centrifugal direction thereof.

Abstract: A water-cooled internal combustion engine includes a water pump having a short pump drive shaft for reducing the weight and size thereof. In a water-cooled internal engine equipped with a clutch at the end of a crankshaft, a water pump having a water pump drive shaft parallel to the crankshaft is disposed on the axial inside of the clutch, that is, on a central side of the crankshaft.

Abstract: A lubricating system for an internal combustion engine in which oil in a crankcase is supplied into an oil tank by a scavenging pump wherein it is possible to reduce the size of an engine body and the size of the scavenging pump. An oil tank is provided in an engine body adjacent, in the direction along the axis of a crankshaft, to a centrifugal clutch contained in a clutch containing chamber communicating with the inside of a crank chamber. A wall portion for partitioning the inside of the oil tank and the clutch containing chamber from each other is provided with an opening portion for communication between the clutch containing chamber and the inside of the oil tank, the opening portion being located on the outer side relative to the outermost rotational locus of a centrifugal clutch as viewed in the direction along the axis of the crankshaft.

Abstract: A transmission assembly includes a shift drum operable to rotate in first and second directions. The shift drum includes a common speed change position, where both a fastest forward gear and a reverse gear are capable of becoming engaged, in such a manner that a reverse stopper arm fits at a first end of a reverse cam groove formed on the shift drum. When the shift drum is rotated in the second rotation direction, opposite to the first direction, from a state where the reverse gear is engaged, the reverse stopper arm surmounts the outer periphery of the shift drum from the first end of the reverse cam groove, without requiring the application of an external force thereto, so as to become detached and to move towards a second end of the reverse cam groove.

Abstract: A vehicle transmission includes first and second main shafts that enable switching of power transmission from an engine; a counter shaft connected to a drive wheel; and gear trains with a plurality of shift stages provided between each of the first and second main shafts and the counter shaft. The vehicle transmission also includes shifters which switch between engagement with and disengagement from a gear constituting part of each of the gear trains so as to switch the established states of the gear trains, and to prevent, during running at the most frequently used shift stage, the occurrence of gear rattle produced by a gear train other than the gear train with such a shift stage. With this configuration, in the running state of using a particular gear train with the highest frequency of the established states among the gear trains, the gear trains, excluding the particular gear train, are in the non-established state.

Abstract: A water-cooled internal combustion engine configured so as to facilitate the change of the cooling system, thereby reducing costs. The crankcase of the water-cooled internal combustion engine is adapted to journal a crankshaft. The crankcase is covered by a crankcase cover from the axial outside. The crankcase is connected to the crankcase cover through an annular shaped spacer, and at least part of a water pump is formed integrally with the spacer.

Abstract: To reduce the engaging sound to a low level, generated at the time of changing over the change gear stage by sliding a shifter, an intermittent feed mechanism includes a drum shifter, a pair of pawls symmetrically mounted to the drum shifter and energized in tilting-up directions, engaging recesses provided at regular intervals along the circumferential direction at the inner periphery of a shift drum center so as to be capable of engagement with both the pawls, and a fixed guide plate for guiding the tilted conditions of both the pawls. The guide plate is provided with a large-diameter arcuate part, a small-diameter arcuate part, and connecting parts. The pawls are engaged with the engaging recesses by the connecting parts, in the course of turning of the drum shifter by a turning amount necessary for changing over the establishment conditions of a plurality of change gear stages of gear trains.

Abstract: A vehicular transmission for an internal combustion engine includes lead grooves disposed on an outer periphery of a shift drum have communication portions connecting a pair of gear train establishment portions extending circumferentially along the shift drum. The communication portions include half neutral portions formed at a center thereof, extending circumferentially along the shift drum. The resulting configuration suppresses an engagement noise to a minimum during changing of a gear position through a sliding motion of a shifter.

Abstract: A vehicular transmission includes a shift drum center with a plurality of gear train establishment notches disposed, equally spaced apart from each other, on the outer periphery thereof. The gear train establishment notches establish a specific gear train selected from among a plurality of gear trains by selectively engaging a drum stopper arm therein. The shift drum center further includes half neutral notches to be engaged with the drum stopper arm. The half neutral notches are disposed on the outer periphery of the shift drum center and at a central portion between each pair of the gear train establishment notches, respectively. The resulting configuration effectively suppresses an engagement noise during changing of a gear position through a sliding motion of a shifter.

Abstract: A power unit provided with a dry sump type lubricating device includes a power unit case that is covered in part by a power unit case cover and is divided into a front unit case and a rear unit case. The power unit also includes a crankshaft rotatably supported by a crank chamber that is formed by the power unit case and a shift shaft rotatably supported by a transmission chamber that is provided adjacent to the crank chamber. The power unit also includes an oil tank disposed on the crank chamber side of an anteroposterior outside surface of the power unit case cover and a hydraulic control device for controlling a shift clutch, disposed on the transmission chamber side of the anteroposterior outside surface of the power unit case cover.

Abstract: A starting clutch includes a clutch inner that is secured to and supported by a drive plate boss fitted to a crankshaft near the end thereof. A one-way clutch is fitted to the outer periphery of the cylindrical portion extending inwardly. A clutch outer forms an annular portion that covers the outer periphery of the drive plate. A hollow disk portion covers the inner surface and is rotatably supported by the crankshaft. The one-way clutch is clamped by the inner peripheral edge of the hollow disk portion of the clutch outer from the outer peripheral side in cooperation with the cylindrical portion of the drive plate boss, and the inner peripheral edge of the hollow disk portion of the clutch outer abuts against a flange portion of the drive plate boss extending along the inner surface of the drive plate in the centrifugal direction thereof.

Abstract: A lubricating system for an internal combustion engine in which oil in a crankcase is supplied into an oil tank by a scavenging pump wherein it is possible to reduce the size of an engine body and the size of the scavenging pump. An oil tank is provided in an engine body adjacent, in the direction along the axis of a crankshaft, to a centrifugal clutch contained in a clutch containing chamber communicating with the inside of a crank chamber. A wall portion for partitioning the inside of the oil tank and the clutch containing chamber from each other is provided with an opening portion for communication between the clutch containing chamber and the inside of the oil tank, the opening portion being located on the outer side relative to the outermost rotational locus of a centrifugal clutch as viewed in the direction along the axis of the crankshaft.