Abstract: A fuel tank is disposed under a flat footboard. A vehicle body cover is disposed laterally of the fuel tank. An opening introduces travelling wind to a space between the fuel tank and the vehicle body cover. A first exhaust pipe is located upstream of a catalyst and is connected to an exhaust port. A catalyst housing portion accommodates the catalyst, is connected to the first exhaust pipe, and extends backwardly from the first exhaust pipe. A second exhaust pipe is located downstream of the catalyst, is connected to the catalyst housing portion, extends backwardly from the catalyst housing portion, and is connected to a silencer. The first exhaust pipe at least partially overlaps with the fuel tank in a vehicle front view. The catalyst housing portion is at least partially disposed rearward of the space between the fuel tank and the vehicle body cover.

Abstract: A single-cylinder internal combustion engine includes a knock sensor mounted thereto to suppress a temperature increase of the knock sensor and at the same time detect knocking with high accuracy. The engine includes a cylinder block having a cylinder provided therein, and a cylinder head connected to the cylinder block. On a surface of the cylinder block and the cylinder head, one or more fins protruding from the surface are provided. On the surface of the cylinder block, a sensor mounting boss protruding from the surface and being continuous with a portion of the one or more fins is provided. A knock sensor arranged to detect knocking is mounted to the sensor mounting boss.

Abstract: In a single-cylinder internal combustion engine fitted with a knock sensor, a temperature increase of the knock sensor is suppressed and prevented, and the reliability of the knock sensor is improved. The engine includes a crankcase, a cylinder block connected to the crankcase, a cylinder head connected to the cylinder block, a sensor mounting boss provided on the cylinder block, and a knock sensor mounted to the boss. Fins are provided on the cylinder block and the cylinder head. A heat insulation member is provided between the boss and the knock sensor.

Abstract: In a single-cylinder internal combustion engine fitted with a knock sensor, a temperature increase of the knock sensor is suppressed and prevented and the reliability of the knock sensor is improved. The engine includes a crankcase accommodating a crankshaft, a cylinder block connected to the crankcase and including a cylinder provided therein, a cylinder head connected to the cylinder block, a sensor mounting boss provided on the cylinder block, a knock sensor arranged to detect knocking and mounted to the boss, a fan to guide air to at least the sensor mounting boss, and an air shroud.

Abstract: A single-cylinder internal combustion engine includes a knock sensor mounted to apart other than a cylinder block to detect knocking. The engine includes a crankcase, a cylinder block, and a cylinder head connected by a bolt. A boss to mount the knock sensor is provided on the crankcase. A center of the boss is positioned on a same side of a cylinder axis as the bolt, when viewed in an axial direction of the boss.

Abstract: A fuel tank is disposed under a flat footboard. A vehicle body cover is disposed laterally of the fuel tank. An opening introduces travelling wind to a space between the fuel tank and the vehicle body cover. A first exhaust pipe is located upstream of a catalyst and is connected to an exhaust port. A catalyst housing portion accommodates the catalyst, is connected to the first exhaust pipe, and extends backwardly from the first exhaust pipe. A second exhaust pipe is located downstream of the catalyst, is connected to the catalyst housing portion, extends backwardly from the catalyst housing portion, and is connected to a silencer. The first exhaust pipe at least partially overlaps with the fuel tank in a vehicle front view. The catalyst housing portion is at least partially disposed rearward of the space between the fuel tank and the vehicle body cover.

Abstract: A centrifugal clutch is disclosed. The centrifugal clutch has a first plate provided in a clutch housing, a second plate provided in a clutch boss, a pressure plate capable of being moved close to and away from the first and second plates, and a centrifugal weight arranged to push the pressure plate toward the first and second plates by receiving centrifugal force. The centrifugal clutch is arranged so that torque T transmitted between the first and second plates is temporarily reduced and then increased as an engine rotational speed is increased from a time when an engine is stopped.

Abstract: A straddle-type vehicle is disclosed. The straddle-type vehicle has a planetary gear mechanism having a ring gear rotatable with a crankshaft, a sun gear, and at least two planetary gears. The straddle-type vehicle also has a planetary carrier, a rotary shaft rotating with the sun gear, an output shaft rotating with the planetary carrier, and a CVT having a primary shaft rotatable with the rotary shaft. The straddle-type vehicle further has a primary pulley, a secondary shaft rotatable with the crankshaft, a secondary pulley, and a belt. The straddle-type vehicle additionally has an actuator configured to change a transmission gear ratio of the CVT. The crankshaft, the planetary gear mechanism, the rotary shaft, and the belt-type continuously variable transmission form a cyclic power transmission passage. A centrifugal clutch is disposed within the passage.

Abstract: A centrifugal clutch is provided with a clutch housing, a clutch boss, a plate group, a pressure plate, a roller retainer, a disc spring, a pressing body and a clutch release mechanism. The pressure plate is displaced on one side in the direction of an axis line and configured to directly or indirectly press the plate group and transition the same into a pressed-contact state. The disc spring extends in a direction of being inclined to the direction of the axis line from a first end portion toward a second end portion in a centrifugal direction. The first end portion of the disc spring is directly or indirectly fixed to the clutch housing. The second end portion of the disc spring directly or indirectly biases the roller retainer toward the plate group.

Abstract: A straddle-type vehicle is disclosed. The straddle-type vehicle has a planetary gear mechanism having a ring gear rotatable with a crankshaft, a sun gear, and at least two planetary gears. The straddle-type vehicle also has a planetary carrier, a rotary shaft rotating with the sun gear, an output shaft rotating with the planetary carrier, and a CVT having a primary shaft rotatable with the rotary shaft. The straddle-type vehicle further has a primary pulley, a secondary shaft rotatable with the crankshaft, a secondary pulley, and a belt. The straddle-type vehicle additionally has an actuator configured to change a transmission gear ratio of the CVT. The crankshaft, the planetary gear mechanism, the rotary shaft, and the belt-type continuously variable transmission form a cyclic power transmission passage. A centrifugal clutch is disposed within the passage.

Abstract: A centrifugal clutch is disclosed. The centrifugal clutch has a first plate provided in a clutch housing, a second plate provided in a clutch boss, a pressure plate capable of being moved close to and away from the first and second plates, and a centrifugal weight arranged to push the pressure plate toward the first and second plates by receiving centrifugal force. The centrifugal clutch is arranged so that torque T transmitted between the first and second plates is temporarily reduced and then increased as an engine rotational speed is increased from a time when an engine is stopped.

Abstract: A friction clutch has a clutch housing including a friction plate, a clutch boss including a clutch plate, and a pressure plate causing the friction plate and the clutch plate to contact each other by moving in a predetermined direction. A clutch spring applies a biasing force in a direction of causing the pressure plate to press the friction and clutch plates into contact with each other. An annular retainer receives a reaction force to the biasing force of the clutch spring by supporting one end of the clutch spring opposite to the pressure plate. A circlip of a notched ring shape is fitted into an inner peripheral side of the clutch housing. The circlip locks the retainer to the clutch housing by abutting on an opposite side of the retainer. The retainer is configured to suppress radially inward deformation of the circlip when a vehicle engine is driven.

Abstract: A single-cylinder internal combustion engine includes a knock sensor mounted thereto to suppress a temperature increase of the knock sensor and at the same time detect knocking with high accuracy. The engine includes a cylinder block having a cylinder provided therein, and a cylinder head connected to the cylinder block. On a surface of the cylinder block and the cylinder head, one or more fins protruding from the surface are provided. On the surface of the cylinder block, a sensor mounting boss protruding from the surface and being continuous with a portion of the one or more fins is provided. A knock sensor arranged to detect knocking is mounted to the sensor mounting boss.

Abstract: In a single-cylinder internal combustion engine fitted with a knock sensor, a temperature increase of the knock sensor is suppressed and prevented and the reliability of the knock sensor is improved. The engine includes a crankcase accommodating a crankshaft, a cylinder block connected to the crankcase and including a cylinder provided therein, a cylinder head connected to the cylinder block, a sensor mounting boss provided on the cylinder block, a knock sensor arranged to detect knocking and mounted to the boss, a fan to guide air to at least the sensor mounting boss, and an air shroud.

Abstract: A single-cylinder internal combustion engine includes a knock sensor mounted to apart other than a cylinder block to detect knocking. The engine includes a crankcase, a cylinder block, and a cylinder head connected by a bolt. A boss to mount the knock sensor is provided on the crankcase. A center of the boss is positioned on a same side of a cylinder axis as the bolt, when viewed in an axial direction of the boss.

Abstract: In a single-cylinder internal combustion engine fitted with a knock sensor, a temperature increase of the knock sensor is suppressed and prevented, and the reliability of the knock sensor is improved. The engine includes a crankcase, a cylinder block connected to the crankcase, a cylinder head connected to the cylinder block, a sensor mounting boss provided on the cylinder block, and a knock sensor mounted to the boss. Fins are provided on the cylinder block and the cylinder head. A heat insulation member is provided between the boss and the knock sensor.

Abstract: According to some preferred embodiments, a clutch housing (46) of a clutch (2) has a bottom portion (46a) in a closed-end cylindrical shape, a plurality of arms (46d) extending along an axial direction from the bottom portion (46a) and provided along a circumferential direction centering on an axial center (C) of the clutch shaft (33), and a plurality of gaps (46e) formed between adjacent arms (46d). Off-springs (71) are arranged in the gaps and extend along the axial direction.

Abstract: A clutch 44 has a clutch boss 441, a clutch housing 442, a friction plate 64, a clutch plate 65, and a pressure plate 450. The clutch boss 441 is attached to the main shaft 41 so as to be integrally rotated therewith. The clutch housing 442 encloses the periphery of the clutch boss 441 and is attached to the main shaft 41 so as to be rotated with respect to the main shaft 41. The friction plate 64 has a plate main body and a friction material and rotates together with the clutch housing 442. The clutch plate 65 faces the plate main body via the friction material and rotates together with the clutch boss 441. The pressure plate 450 rotates together with one of the clutch boss 441 the clutch housing 442 which is engaged with the friction plate 64.

Abstract: A cam face 81 and a cam face 181 are formed in such a manner that an angular velocity ? represented by the following equation increases when a parameter R increases and the angular velocity ? decreases when the parameter R decreases, ?2=(1/m)·[F(tan ?+tan ?)/R], where the mass of the centrifugal weight (41) is m, the revolution radius that is the distance from the rotation center (0) of the centrifugal weight (41) to the center of gravity of the centrifugal weight (41) is R, the angle formed by a radial line (L0) and a tangent line (L1) of a point of the cam face (81) being in contact with the centrifugal weight (41) is ?, the angle formed by a radial line (L0) and a tangent line (L2) of a point in the cam face (181) being in contact with the centrifugal weight (41) is ?, and the urging force of a Belleville spring that urges a roller retainer (78) is F.

Abstract: A clutch structure, constructed without a one-way clutch, remains engaged until the input side rotational speed becomes relatively low. A pressure plate presses a group of plates directly or indirectly by moving in the direction of an axis, bringing the group of plates into a press contact state. An input side press body turns around the axis with the rotation of a clutch housing, presses the pressure plate to the side of the group of plates by centrifugal force generated during the turning, and moves in a direction away from the axis. A roller retainer presses the group of plates directly or indirectly by moving in the direction of the axis, bringing the group of plates into a press contact state. An output side press body turns around the axis with the rotation of an output side clutch member, presses the roller retainer to the side of the group of plates by centrifugal force generated during the turning, and moves in a direction away from the axis.