Abstract: The cartridge type transmission is a transmission configured to be detachable and attachable from/to the crankcase, the main shaft is arranged on the cut surface BF of the crankcase, and the change spindle and the shift fork shaft are pivotally supported in the upper crankcase, which is positioned on the upper side of the cut surface BF. The counter shaft is pivotally supported in the lower crankcase, which is positioned on the lower side of the cut surface BF.

Abstract: To miniaturize an engine, to concentrate heavy masses and to reduce friction loss of a balancer. An engine crankcase structure in which a crankcase is vertically partitioned into an upper case and a lower case, each journal supporter is formed in the upper case and in the lower case so that the rotational axis of a crankshaft is located on a partition face of the crankcase in parallel with a direction of the width of the body. The crankshaft is supported so that the crankshaft can be rotated. An oil filter is directly attached to the lower case. An oil cooler and a secondary balancer are arranged in the front of the lower case.

Abstract: To advance the pivotally supporting point of a swing arm on a vehicle body frame, the distance in the forward and backward direction between a crankshaft and a countershaft of a transmission is decreased as much as possible thereby making the length of the swing arm great and sufficiently absorb upward and downward oscillation of a rear wheel to achieve stabilization of the vehicle body.

Abstract: By blocking off a partial passage opening in a lubricating oil supply passage of a transmission gear mechanism by attaching a transmission holder, an operation to block off the passage opening is omitted. Supply of lubricating oil to a main shaft and a counter shaft of a transmission gear mechanism is carried out using branched passages from a main gallery, and the branched passage constitutes a lubricating oil supply passage to the main shaft while the branched passage constitutes a lubricating oil supply passage to the counter shaft. A partial passage opening of the branched passage is then blocked up at the time of attaching a transmission holder to the transmission case, and in this way a lubricating oil supply passage to the counter shaft is formed.

Abstract: A cylinder head, for an internal combustion engine, enhances engine efficiency while ensuring favorable coolant flow. The cylinder head includes a main casting body 41 having a hollow water jacket formed therein, to allow coolant flow therethrough. The main casting body 41 includes a plurality of cylindrical plug hole walls 91 which have plug holes 90 formed therein inside a head-side water jacket 60. The cylinder head also includes partitions 100, formed inside the head-side water jacket 60, and these partitions connect the plug hole walls 91 together form a dividing wall, which divides the water jacket into an exhaust port section and an intake port section. Coolant entering the water jacket is divided into two substreams, which flow initially in substantially opposite directions, and which are reunited after flowing around opposite ends of the dividing wall.

Abstract: A threaded fastener is configured to reduce stress experienced at a female threaded portion of a hole formed in an engine block, when the threaded fastener is inserted therein, and when an axial load is applied thereto. In a particular application, a crankshaft is supported between a top supporting wall of a crankcase and a bottom supporting wall of a main cap. The inventive bolt includes a hollowed-out male threaded portion, which fits into a hole in the top supporting wall. The male threaded portion includes an elastically deformable low-rigidity portion, in which a cylindrical hole is concentrically formed. The maximum allowable stress of the top supporting wall is less than that of the bolt, due to material considerations. The low-rigidity portion is placed overlapping the female threaded portion in the axial direction, and since it is elastically deformable, it helps alleviate the stress experienced by the female threaded portion.

Abstract: To facilitate attachment/detachment work of an oil filter in a vehicle engine without increasing an outer dimension thereof, and to provide a uniform a supply of engine oil into an engine body. An oil filter is attached onto a front portion of the engine body so as to be detachable in a vehicle body width direction from a side face of the engine body. An exhaust pipe on a side on which an oil filter is attached is displaced to a center side in the vehicle body width direction so as not to overlap the oil filter when viewed from a front of the engine body.

Abstract: A multi-cylinder internal combustion engine draws oil from an oil reservoir with an oil pump, and supplies oil to individual areas of the engine, after passing the oil through an oil filter and an oil cooler. A filter case containing an element of the oil filter is mounted to a side surface of the engine to facilitate the removal and replacement of the case. The oil cooler and a balancer are each respectively mounted to a front central portion of the internal combustion engine to enable oil cooling by an air-cooling effect of a running airflow, and to balance weight in the left-right direction of the internal combustion engine. Oil discharged from the oil cooler is introduced to a substantially central portion of the main gallery, to achieve uniformity of oil pressure supplied to individual bearing portions and uniformity of cooling of the individual bearing portions.

Abstract: A gear position detecting system includes structure which facilitates mounting of the system, and minimizes direct contact of other objects with the system. The outer circumferential surface of a shift drum, turned by operation of a change pedal, is provided with lead grooves. Shift forks, engaged with the lead grooves, are moved in the left-right direction by turning of the shift drum, whereby shift gears are changed over, and a speed change desired by the rider is performed. A detection pin of a neutral safety switch, which is one of gear position sensors, is pushed in by a detection cam of a cam surface provided at the outer circumferential surface of the shift drum in the speed change operation position, whereby a neutral position is detected.