A hybrid power assembly and an all-terrain vehicle are provided. The hybrid power assembly includes an engine and a motor. The engine includes a crankshaft and a crankcase, the crankshaft is mounted in the crankcase, the crankcase includes a motor mounting cap, and a first end of the crankshaft extends out of the motor mounting cap. The motor includes a motor housing, a cap of the motor, a stator, and a rotor. The motor housing is mounted between the motor mounting cap and the cap of the motor, the stator is fixed in the motor housing, the rotor is arranged on the inner circwnference of the stator and is rotatable relative to the stator, and the rotor is connected to the first end of the crankshaft.

A vehicle power unit has a transmission apparatus including a transmission, and a transmission actuating mechanism including a speed reduction gear train having multiple speed reduction stages for transmitting power from a drive gear on a drive shaft of a shift motor to a driven gear on a drum turning shaft of a shift drum. The speed reduction gear train has a speed reduction ratio ranging from 23 to 45, and the shift motor is a DC electric motor that produces a pulsating cogging torque having a maximum value ranging from 0.04 to 0.07 Nm. The vehicle power unit enables the transmission actuating mechanism to be made up of a reduced number of parts and to be simple in structure, making the transmission apparatus small in size, and ensures quicker and smoother gear changes with an electric motor.

A power end assembly includes a crankshaft section, a crosshead section, and a connector section coupled together by one, two, or more sets of stay rods. The power end may include one or more support plates that are coupled to the crankshaft section and/or crosshead section. The crosshead section includes a plurality of individual crosshead frames. The connector section may include a plurality of individual connector plates or may be a unitary connector plate. The power end is configured to be coupled to a fluid end assembly by coupling the fluid end assembly to the connector plates.

A power unit includes: a crankcase which accommodates a crankshaft and a main shaft arranged in parallel to each other; a crank side cover which covers one end portion of the crankshaft from the outside in an axial direction of the crankshaft; a primary driven gear which is provided in the main shaft and meshes with a primary drive gear of the crankshaft; a clutch provided at one end portion of the main shaft; and a clutch cover which covers the clutch from the outside in an axial direction of the main shaft and is fastened and fixed to a packing surface provided on the crankcase to surround the clutch, wherein the primary driven gear and the packing surface overlap in a virtual straight line when viewed from the axial direction of the main shaft.

In a vehicle power unit, a drum rotary shaft member on one side of a shift drum is provided with a driven gear. A case side wall on one side of an engine crankcase supporting the drum rotary shaft member is covered by a case cover member in opposing relation thereto. A shift motor is mounted to the case cover member, with a driving gear thereof directed to protrude toward the case side wall. A speed reducing gear train has gear shafts and provides a multiplicity of speed reduction stages for transmitting power from the driving gear to the driven gear. The speed reducing gear train is arranged with both ends of its gear shafts thereof supported on the case side wall and the case cover member, respectively. Such arrangement provides a vehicle power unit for a fast and smooth shift by an electric motor.

A structure of an engine transmission box is provided. The transmission box includes a transmission box body and a cover arranged on and covering the transmission box body. The transmission box includes at least one airflow entrance opening and an air outlet opening. The cover includes an air inlet port portion, which has an air inlet opening, and a filter member arranged outside of the air inlet opening. An airflow guide hood is arranged to cover the air inlet port portion. The filter member is located between the airflow guide hood and the air inlet port portion. With such an arrangement, a space is guaranteed inside the transmission box, and cleaning or replacement engineering of the filter member is made easy.

A structure of an engine transmission box is provided. The transmission box includes a transmission box body and a cover arranged on and covering the transmission box body. The transmission box includes at least one airflow entrance opening and an air outlet opening. The cover includes an air inlet port portion, which has an air inlet opening, and a filter member arranged outside of the air inlet opening. An airflow guide hood is arranged to cover the air inlet port portion. The filter member is located between the airflow guide hood and the air inlet port portion. With such an arrangement, a space is guaranteed inside the transmission box, and cleaning or replacement engineering of the filter member is made easy.

As viewed from a side, an output shaft is disposed rearward of a crankshaft, and an odd-numbered stage shaft and an even-numbered stage shaft are disposed rearward of the crankshaft. Moreover, the odd-numbered stage shaft is provided on a side opposite to the even-numbered stage shaft relative to a line connecting the crankshaft and the output shaft, and a shift drum is disposed on a side opposite to the output shaft relative to a line connecting the odd-numbered stage shaft and the even-numbered stage shaft. This structure reduces dimensions of the power unit for the saddled vehicle.

A gear housing assembly includes a gear housing and a gear cover for an internal combustion engine. The gear housing includes gear housing drillings, the gear cover includes gear cover drillings, wherein the gear cover is attached to the gear housing such that one of the gear cover drillings is fluidly connected with one of the gear housing drillings via a gasketed interface to supply oil through a debris screen to two fuel pumps mounted on the gear housing. A serviceable access cover is mounted on the gear cover. An idler gear is assembled onto an idler shaft to form a sub-assembly, wherein the idler gear is positioned between the serviceable access cover and the gear housing. The idler shaft is supported by the bushing in the access cover and two bushings mounted in the gear housing to provide radial and thrust load bearing capabilities.

In a transmission apparatus for a saddle-type vehicle, dowels on first transmission gears are engageable in and disengageable from dowel holes in adjacent second transmission gears to shift gear positions. The first transmission gears are slidable in response to angular movement of a shift spindle caused by operating a shift pedal. Invalid engagement time, during which the dowels and dowel columns are in sliding abutment, at an idling engine rotational speed is in the range from 0 msec. to 40 msec., providing an enhanced feeling for gear shifting operations and reduce hammering noise.