Abstract: An exhaust structure for an engine includes: a catalyst converter configured to purify exhaust gas of the engine; a catalyst pipe in which the catalyst converter is accommodated; and a lead-out pipe configured to lead the exhaust gas to the catalyst pipe. The lead-out pipe is closed at a downstream end thereof, and has a plurality of discharge holes formed in a peripheral wall thereof.

Abstract: A straddle-type vehicle comprises an engine which generates driving power and emits an exhaust gas; an exhaust device including: a catalyst which cleans the exhaust gas, an inner tube in which the catalyst is disposed and through which the exhaust gas flows, the inner tube extending to a location downstream of the catalyst; and an outer tube which covers an outer peripheral surface of the inner tube in an axial direction of the inner tube, and has a muffling space through which the exhaust gas discharged from the inner tube is flowed to reduce an exhaust noise radiated from the engine; at least one exhaust pipe through which the exhaust gas is led to the catalyst; and a downstream oxygen sensor which detects an oxygen concentration of the exhaust gas after flowing through the catalyst, at a location downstream of the catalyst in the inner tube.

Abstract: A motorcycle supercharger (42) pressurizes intake air (I) for a combustion engine (E). The supercharger (42) includes a centrifugal impeller (50) and an impeller casing (52) which covers the impeller (50). The impeller casing (52) includes an outer peripheral wall (84) located radially outward of the impeller (50) and a side wall (86) located axially outward of the impeller (50). Reinforcing first and second side wall ribs (94, 96) are provided at the side wall (86) of the impeller casing (52).

Abstract: An impeller for pressurizing an intake air of an engine is provided on a left side end portion in a supercharger rotary shaft of the supercharger. The power from the engine is transmitted to a second sprocket, which is provided on a right side end portion of an input shaft of a speed increaser, through a chain to thereby allow the supercharger to drive. The second sprocket is removably fitted to the input shaft by means of a bolt. The supercharger rotary shaft, the input shaft, the second sprocket and the bolt are all accommodated in a supercharger casing. The supercharger casing has a right side end face formed with an access opening through which access can be made to the second sprocket and the bolt from an axial direction.

Abstract: A power transmission system includes an input shaft, a supercharger rotary shaft disposed coaxially with the input shaft, and a transmission mechanism interposed between the input shaft and the supercharger rotary shaft. A lubricating structure of the power transmission system is provided with an injection passage through which a portion of oil for lubricating bearings for supporting the supercharger rotary shaft is supplied, from a supercharger casing for supporting the bearings, towards the input shaft by means of a jetting spray across an interior space within the transmission mechanism.

Abstract: Out of a plurality of speed change gears on one of an input shaft and an output shaft, for example, on the output shaft, two adjacent speed change gears disposed via an axial space therebetween are axially fixed and rotatably fitted around the output shaft. A dog ring for a dog clutch disposed between the speed change gears is fixed around the output shaft and axially slidably fitted thereto. The speed change gears on the output shaft and the dog ring are each provided with an engagement portion for the dog clutch engaged and disengaged by axial shift of the dog ring. The two speed change gears on the input shaft meshing with the two speed change gears on the output shaft are provided integrally with the input shaft.

Abstract: A supercharging system for a combustion engine of a motorcycle includes a supercharger which pressurizes intake air and supplies the intake air to the combustion engine, an air intake chamber which is connected to downstream of the supercharger, a relief passage which relieves the high-pressure intake air within the air intake chamber, and a relief valve which is provided on the relief passage. The air intake chamber is disposed above the combustion engine, and the relief passage is disposed below an upper end of the air intake chamber. The relief passage is connected to a front surface of the air intake chamber.

Abstract: A combustion engine for a motorcycle includes a supercharger which pressurizes intake air. The supercharger is driven by power of the combustion engine. A first cushioning body which suppresses rotation fluctuation of power is provided on a power transmission path leading from the combustion engine to the supercharger. The first cushioning body has a damper structure to transmit power from an upstream side to a downstream side thereof through an elastic body.

Abstract: An oil filter and an oil cooler of a motorcycle combustion engine are disposed on an outer surface of an engine body side by side in a right-left direction. A first engine lubrication passage extending in the right-left direction is connected to an outflow passage for the oil cooler. A second engine lubrication passage is connected to the first engine lubrication passage, to extend frontward, and is disposed parallel to an inflow passage and an outflow passage for the oil filter. A third engine lubrication passage is connected to the second engine lubrication passage and extends upward from the second engine lubrication passage in front of the first engine lubrication passage.

Abstract: A rotary unit is rotatably accommodated within a supercharger casing of a supercharger for pressurizing an intake air of an engine. The rotary unit includes a supercharger rotary shaft, an impeller fixed to a tip end portion of the supercharger rotary shaft, a rotating component rotatable together with the supercharger rotary shaft independently of the impeller, and a nut member for pressing the impeller and the rotating component in a direction axially of the supercharger rotary shaft to thereby fix them to the supercharger rotary shaft. The nut member is formed with an adjustment portion for the rotational balance adjustment.

Abstract: A motorcycle includes a supercharger to pressurize an intake air and supplying it to a combustion engine and an air intake chamber disposed downstream of the supercharger. The air intake chamber is made of a metallic material and has a capacity of an interior space thereof which is within the range of three to eight times the displacement of the combustion engine. The dimension from an upstream end portion on an inlet side of the interior space of the air intake chamber to a downstream end portion on an outlet side of the interior space of such air intake chamber is chosen to be three or more times the inner diameter of an outlet.

Abstract: An air intake chamber is disposed at a location downstream of a supercharger and upstream of a throttle body. The air intake chamber serves to accumulate an intake air pressurized by the supercharger. This air intake chamber includes a confronting portion, which has an outlet and overlaps the throttle body, and a connecting portion that connects between the confronting portion and a discharge port of the supercharger. The connecting portion has an outlet side opening set to be larger than an inlet side opening thereof.

Abstract: An air intake duct of a motorcycle extends rearwardly from a front portion of a motorcycle body so as to pass laterally of the left side of a motorcycle frame structure, and incoming wind is supplied as an intake air through the air intake duct to a combustion engine. The air intake duct is divided in a widthwise direction of the motorcycle. An upper dividing face of the air intake duct is disposed inward of an intermediate position, in a motorcycle widthwise direction, of the air intake duct.

Abstract: A piston cooling structure for an engine includes a first nozzle and a second nozzle for injecting a cooling liquid towards a back face of a piston that reciprocally move within a cylinder bore along a cylinder axis line. The first angle of inclination of an axis of the first nozzle relative to the cylinder axis line is set to be smaller than the second angle of inclination of an axis of the second nozzle relative to the cylinder axis line.

Abstract: A straddle-type vehicle comprises an engine which generates driving power and emits an exhaust gas; an exhaust device including: a catalyst which cleans the exhaust gas, an inner tube in which the catalyst is disposed and through which the exhaust gas flows, the inner tube extending to a location downstream of the catalyst; and an outer tube which covers an outer peripheral surface of the inner tube in an axial direction of the inner tube, and has a muffling space through which the exhaust gas discharged from the inner tube is flowed to reduce an exhaust noise radiated from the engine; at least one exhaust pipe through which the exhaust gas is led to the catalyst; and a downstream oxygen sensor which detects an oxygen concentration of the exhaust gas after flowing through the catalyst, at a location downstream of the catalyst in the inner tube.

Abstract: An engine (E) of a saddle-riding type vehicle has an engine case that is substantially L-shaped by a cylinder block (42) being protruded upward from an upper face of a front portion of a crank case (40). An air cleaner (55) is disposed rearwardly of the cylinder block (42) and above the crank case (40). An outlet (72) through which blow-by gas (G) in the engine (E) is discharged is formed in the rear portion of the cylinder block (42). A case body (84) of the air cleaner (55) has a blow-by gas introduction port (86) through which the blow-by gas (G) is introduced into the air cleaner (55). The outlet (72) of the cylinder block (42) and the blow-by gas introduction port (86) of the case body (84) are connected by a connecting pipe (90). The blow-by gas introduction port (86) is disposed close to the cylinder block (42).

Abstract: A combustion engine of a motorcycle has an engine rotary shaft extending in a vehicle widthwise direction. Incoming wind taken in from a front of a steering handle that is positioned in front of the combustion engine, is introduced through an air intake duct to the combustion engine. The air intake duct extends from the front of the steering handle to a rearward of a cylinder block so as to pass above a radiator and pass laterally of one side of the cylinder block.

Abstract: An air intake duct, of a saddle-riding type vehicle, in which a flow velocity of an intake air is less likely to be reduced to enable prevention of reduction of an efficiency of a supercharger, is provided. The air intake duct of a motorcycle serves to supply incoming wind as the intake air to the supercharger for a combustion engine. The air intake duct has a passage area that is gradually reduced from an air intake port at a front portion toward a downstream portion connected to the supercharger at a rear portion.

Abstract: An air intake chamber for a motorcycle is disposed downstream of a supercharger, for pressurizing and supplying an intake air to an engine, and upstream of a throttle body, for controlling the amount of the intake air to be supplied to an air intake port of the engine. The air intake chamber serves to accumulate the high pressure intake air discharged from the supercharger. The air intake chamber is provided with an injector, which has a fuel injecting port positioned at a location displaced from an axis of an outlet of the air intake chamber.

Abstract: An air intake duct of a motorcycle forms an air intake passage for supplying an intake air to a supercharger. The air intake duct forms a curve portion and is connected to the supercharger. The air intake passage has a transverse cross-section which is shaped such that a dimension in an orthogonal direction that is orthogonal to a radial direction of the curve portion is gradually reduced from the center of the curve portion toward an outer side, in the radial direction, of the curve portion.