A straddled vehicle engine unit including an internal combustion engine and a misfire detection device. The misfire detection device includes a crankshaft rotation speed fluctuation physical quantity acquisition unit and a misfire determination unit. The misfire determination unit includes first to third determination units. The first determination unit determines whether or not the crankshaft rotation speed fluctuation physical quantity acquired by the crankshaft rotation speed fluctuation physical quantity acquisition unit is greater than a set physical quantity determination reference. The second determination unit determines whether or not a fluctuation pattern constituted by a physical quantity and the crankshaft rotation speed fluctuation physical quantity acquired at least before or after the physical quantity falls within a set misfire pattern range. The third determination unit determines whether a misfire determination is to be set as effective or not, based on results of determination by the first and second determination units.

A straddled vehicle engine unit including an internal combustion engine and a misfire detection device. The internal combustion engine has a crankshaft, and a crank angle signal output unit that periodically outputs a crank angle signal in accordance with rotation of the crankshaft. The internal combustion engine is configured to repeat at least two kinds of strokes on a cycle of every 720-degree rotation of the crankshaft. The misfire detection device includes a crankshaft rotation speed fluctuation physical quantity acquisition unit configured to acquire a physical quantity related to an amount of fluctuation in a rotation speed of the crankshaft in one kind of stroke, out of the at least two kinds of strokes, based on the crank angle signal from the crank angle signal output unit, and a misfire determination unit configured to perform a misfire determination in response to each acquisition of the crankshaft rotation speed fluctuation physical quantity.

In a throttle device including: a throttle shaft to which a throttle valve is secured; a motor; and a deceleration mechanism decelerating rotation of a drive shaft of the motor and transmitting the rotation to the throttle shaft, the deceleration mechanism includes a throttle gear secured to the throttle shaft, the throttle gear includes a tubular ring into which the throttle shaft is detachably inserted and a gear main body including a gear portion, and the gear main body is formed of a resin by insert processing including the ring.

A two-wheeled vehicle includes a frame assembly, a plurality of ground-engaging members for supporting the frame assembly, and a cooling assembly positioned below a head portion of the frame assembly and intermediate vertically-extending frame tubes of the frame assembly. A lower end of the cooling assembly is coupled to a lower end of the vertically-extending frame tubes, and an upper end of the cooling assembly is frictionally retained at an upper end of each of the vertically-extending frame tubes.

A wheelie controller and a control method thereof or preventing a reduction of acceleration that is more than necessary and reducing a shock during a contact of a front wheel with the ground when a wheelie state is terminated. The wheelie controller for controlling a wheelie of a vehicle body computes a target trajectory, which is a target of a parameter and is used to control the wheelie state of the vehicle body, in accordance with the parameter that is related to pitch of the vehicle body and controls an increase/reduction of the pitch of the vehicle body so as to bring the parameter close to the target trajectory.

A wheelie controller and a control method thereof or preventing a reduction of acceleration that is more than necessary and reducing a shock during a contact of a front wheel with the ground when a wheelie state is terminated. The wheelie controller for controlling a wheelie of a vehicle body computes a target trajectory, which is a target of a parameter and is used to control the wheelie state of the vehicle body, in accordance with the parameter that is related to pitch of the vehicle body and controls an increase/reduction of the pitch of the vehicle body so as to bring the parameter close to the target trajectory.

An internal combustion engine includes a crankshaft that is rotatably supported on the crankcase, a cylinder block that is joined to the crankcase and defines a plurality of cylinders in a V-type arrangement in which the cylinders are disposed above a virtual horizontal plane including a rotational axis of the crankshaft and intersect each other at a bank angle, a to-be-detected body that rotates integrally with the crankshaft, and a detection sensor that is mounted from an outside at a position, lower than the virtual horizontal plane, of a front face of the crankcase that receives air flow, is made to face a trajectory of the to-be-detected body, and generates a pulse signal in response to movement of the to-be-detected body. Thereby provided is a structure for disposing a detection sensor that can detect the angular velocity of a crankshaft with high precision in a so-called V-type internal combustion engine.

A throttle device, comprising: a throttle valve (13) disposed in a plurality of intake passages (12) of a throttle body (11); a throttle shaft (14) supporting the throttle valve (13); a motor (15) for driving the throttle valve (13) to open and close through the throttle shaft (14); a rotation transmission mechanism (20) interposed between the motor (15) and the throttle shaft (14); and a position sensor to detect a displacement in the rotation transmission mechanism (20). The rotation transmission mechanism (20) includes a pinion (21) driven by the motor (15) and a control gear (23) interlocked with the pinion (21) and integrally connected to the throttle shaft (14). The position sensor (30) to detect an angular displacement of the control gear (23) and the rotation transmission mechanism (20) are disposed between the plurality of intake passages 12.

A method of operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine with a two stage exhaust valve system includes: providing a control rod mechanically coupled to a governor, so that the governor causes a rotation of the control rod. A first stage exhaust valve, a second stage left exhaust valve, and a second stage right exhaust valve are also controllably linked to the control rod; and operating the second stage left exhaust valve and the second stage right exhaust valve by opening at least one of the second stage left exhaust valve and the second stage right exhaust valve before the first stage exhaust valve is completely open in an overlap operation. Related methods and structures for overlap, and/or stagger, and/or limiter operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine are also described.

A method of operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine with a two stage exhaust valve system includes: providing a control rod mechanically coupled to a governor, so that the governor causes a rotation of the control rod. A first stage exhaust valve, a second stage left exhaust valve, and a second stage right exhaust valve are also controllably linked to the control rod; and operating the second stage left exhaust valve and the second stage right exhaust valve by opening at least one of the second stage left exhaust valve and the second stage right exhaust valve before the first stage exhaust valve is completely open in an overlap operation. Related methods and structures for overlap, and/or stagger, and/or limiter operation of exhaust valves of an adjustable exhaust port 2-stroke motorcycle engine are also described.