Abstract: A cam 13 formed so that cam height and a cam operation angle continuously change, and constituted to be rotated integrally with a camshaft 11 and relatively movable in an axial direction thereof, a valve lifter 20 pressed by a cam surface of the cam 13 to advance and retreat a valve, and an accelerator shaft unit 40 for moving the cam 13 in the axial direction of the camshaft 11 are included. The accelerator shaft unit 40 includes an accelerator shaft 41 placed to be capable of reciprocating in the axial direction of the camshaft, and an accelerator fork 42 supported at the accelerator shaft 41 and engaging with the cam 13, and has an adjust mechanism 70 for finely adjusting a relative position in an axial direction of the accelerator fork 42 with respect to the accelerator shaft 41.

Abstract: A shim attaching and detaching surface has a sectional portion with a smaller diameter than a base circle of a cam surface in a state in which the shim attaching and detaching surface of a cam is located on a tappet roller, and therefore the tappet roller and an arm member can be moved upward. Since an inner side of a top surface of a tappet guide is inclined, if the arm member is tilted along this inclination, one end of the arm member can be raised, and a clearance is formed in a space from a tappet shim. Accordingly, by inserting a slim plate-shaped or rod-shaped jig 128 from the clearance, the tappet shim 37EX can be attached and detached.

Abstract: A shim attaching and detaching surface has a sectional portion with a smaller diameter than a base circle of a cam surface in a state in which the shim attaching and detaching surface of a cam is located on a tappet roller, and therefore the tappet roller and an arm member can be moved upward. Since an inner side of a top surface of a tappet guide is inclined, if the arm member is tilted along this inclination, one end of the arm member can be raised, and a clearance is formed in a space from a tappet shim. Accordingly, by inserting a slim plate-shaped or rod-shaped jig 128 from the clearance, the tappet shim 37EX can be attached and detached.

Abstract: A cam 13 formed so that cam height and a cam operation angle continuously change, and constituted to be rotated integrally with a camshaft 11 and relatively movable in an axial direction thereof, a valve lifter 20 pressed by a cam surface of the cam 13 to advance and retreat a valve, and an accelerator shaft unit 40 for moving the cam 13 in the axial direction of the camshaft 11 are included. The accelerator shaft unit 40 includes an accelerator shaft 41 placed to be capable of reciprocating in the axial direction of the camshaft, and an accelerator fork 42 supported at the accelerator shaft 41 and engaging with the cam 13, and has an adjust mechanism 70 for finely adjusting a relative position in an axial direction of the accelerator fork 42 with respect to the accelerator shaft 41.

Abstract: The power unit for a motorcycle comprising an engine unit having a casing in which a crankshaft and a countershaft are rotatably supported in parallel to each other, and a transmission unit having a casing in which a transmission input shaft and a transmission output shaft are rotatably supported in parallel to each other to define a dry belt drive-type transmission device. The transmission input shaft of the transmission unit is being connected to the countershaft of the engine unit so as to be rotatable together with the countershaft. A cooling fan chamber is provided at a joined portion of the casing of the engine unit to the casing of the transmission unit, said cooling fan chamber is communicated with an inside and outside of the casing of the transmission unit. A cooling fan is disposed in said cooling fan chamber so as to rotate together with the connecting portion of the countershaft and the transmission input shaft in a vicinity of said connection section.

Abstract: A small-sized vehicle such as scooter-type motorcycle includes an engine unit and a power transmission unit coupled to the engine unit to be swingable. The engine unit includes a power generation section, a speed changing section, a first case into which the power generation unit is accommodated and a second case into which the speed changing section is accommodated. The first and second cases are operatively connected to each other as a unit case constituting the engine unit, which is then mounted to a vehicle body.

Abstract: The part of the bodywork between the frame head pipe and the saddle is bent downwards and formed with a low-floor, step board at the bottom thereof. This bodywork is further formed with a tunnel structure forming an engine tunnel which is extended fore and aft and ridged upward around the center of the step board with respect to the left and right direction thereof, defining a step-through space. A pair of lower down tubes and a pair of upper down tubes, both on the right and left sides, are downwardly and rearwardly extended from the head pipe in front of the step-through space so as to frame a fuel tank and radiator, in the upper and lower positions, respectively. The fuel tank, which is arranged above the radiator, has a lower part, namely bulge portion, which bulges downwards over the upper edge of the radiator and toward the rear space of the radiator located below the fuel tank.

Abstract: The power unit for a motorcycle accodring to the present invention comprises an engine unit having a casing in which a crankshaft and a countershaft are rotatably supported in parallel to each other, and a transmission unit having a casing in which a transmission input shaft and a transmission output shaft are rotatably supported in parallel to each other to define a dry belt drive-type transmission device. Said transmission input shaft of the transmission unit is being connected to the countershaft of the engine unit so as to be rotatable together with the countershaft. A cooling fan chamber is provided at a joined portion of the casing of the engine unit to the casing of the transmission unit, said cooling fan chamber is communicated with inside and outside of the casing of the transmission unit. A cooling fan is disposed in said cooling fan chamber so as to rotate together with the connecting portion of the countershaft and the transmission input shaft in a vicinity of said connection section.

Abstract: A small-sized vehicle such as scooter-type motorcycle includes an engine unit and a power transmission unit coupled to the engine unit to be swingable. The engine unit comprises a power generation section, a speed changing section, a first case into which the power generation unit is accommodated and a second case into which the speed changing section is accommodated. The first and second cases are operatively connected to each other as a unit case constituting the engine unit, which is then mounted to a vehicle body.

Abstract: A power assist bicycle includes a front wheel and a rear wheel, a bicycle body frame supporting the front and rear wheels to be rotatable, a saddle mounted to the bicycle body frame on which a rider rides, and a pair of pedals which are operatively connected to each other through a crank shaft, and the bicycle body frame includes a head pipe supporting the front wheel, a main pipe extending obliquely downward in a rearward direction from the head pipe, and a saddle pipe supporting the saddle at an upper end portion thereof in a standing attitude of the bicycle.

Abstract: A power assist apparatus of a power assisted bicycle comprises a crank shaft extending in the transverse direction of the body of the bicycle and rotatably driven by a footpedal-propelling, an electric motor for generating an assist power, a power composition shaft rotatably supported and extending in parallel with the crank shaft, a footpedal-propelling power transmission mechanism for transmitting the footpedal-propelling power to the power composition shaft at a right angle to the axis of the power composition shaft, an assist power transmission mechanism for transmitting the assist power to the power composition shaft at a right angle to the axis of the power composition shaft in the direction opposite to the direction in which the footpedal-propelling power is transmitted, a power composition output mechanism for outputting the rotating power of the power composition shaft to a driven wheel, a moment sensor for sensing a moment difference between two moments acting on the power composition shaft from two

Abstract: A power assist apparatus of a power assisted bicycle comprises a crank shaft to be driven for rotation by a pedaling force, an electric motor for generating an assisting power, a force composition device for composing the pedaling force and the assisting power to output a composed force thereof to a driving wheel side and at the same time for generating two thrust component forces having magnitude proportional to pedaling force and assisting power, a thrust component force magnitude difference detector for detecting the difference in magnitude between the two thrust component forces, and a controller for controlling an output of the electric motor so as to bring the difference in magnitude between the two thrust component forces to "0" and to an optional magnitude difference based on an input from the thrust component force magnitude difference detector.

Abstract: An exhaust timing controller for a two-stroke cycle engine includes an exhaust timing control valve for changing a height of an open edge portion on a top dead center side of an exhaust port opening to an inside wall surface of a cylinder bore in the engine. The exhaust timing control valve moves axially of the cylinder bore by power from an actuator and the exhaust timing is accelerated in response to rotational frequency rises in the engine. The power of the actuator is transformed into an elevating stroke of the exhaust timing control valve by the eccentric motion of an eccentric cam. A slider mechanism for transferring an eccentric motion of the eccentric cam to the exhaust timing control valve is provided between the eccentric cam and the exhaust timing valve. A straightening member extends smoothly from a portion of the exhaust timing control valve, which retracts into the exhaust port, on the downstream side of the exhaust port.

Abstract: A front and rear wheel drive motorcycle includes an engine unit including a cylinder assembly and a crank shaft and first and second speed change belt mechanisms mounted to one end of the crank shaft for driving the front and rear wheels, respectively. The first and second speed change belt mechanisms are operatively connected to first and second speed change gear mechanisms through first and second speed change gear mechanisms through first and second driven pulleys respectively provided to the first and second change belt mechanism. To one end of the crank shaft is mounted a driving pulley means operated in common with the first and second speed change belt mechanisms. The driving pulley means comprises a stationary driving pulley mounted to one end of the crank shaft and operated in common with the first and second speed change belt mechanisms and a pair of movable driving pulleys mounted to one end of the crank shaft with the stationary driving pulley interposed therebetween.

Abstract: A motor bicycle is provided with an article accommodating box for a helmet which is disposed above an upper portion of an engine unit. The article box is provided with a bottom portion extending rearwardly along the upper portion of an intake system connected to the engine unit and the front portion of the bottom portion rises upwardly at the upper rear portion of the engine cylinder head. The box is provided with a cover having an improved solar heat insulation structure by forming an air passage within an upper portion of the cover. The box is further provided with a ventilation member for air circulation within the interior of the box. The box is locked by means of a locking mechanism which is provided with a device for preventing the box cover from being erroneously locked or unlocked. The motor bicycle may be provided with an additional article accommodating box for an extra helmet at a location defined by means of a space between the head pipe, the cowling and the front fork.