A straddle-type vehicle (100) includes a frame (20) and an engine (10) mounted on the frame (20), the engine (10) includes a cylinder head (11) positioned toward the rear end of the frame, and located below a saddle seat (80). The cylinder head laces toward the rear end of the frame, which allows the heated cylinder head of the engine and the exhaust pipe connected to the cylinder head to avoid contact with the vehicle the user's legs while riding the vehicle, so the effect of heat emitted from the cylinder head on the rider's experience is reduced.

An attachment structure for an exhaust gas sensor, wherein an exhaust gas sensor is attached to a downstream connection pipe part of an exhaust pipe so as to be disposed, in a side view of a motorcycle, in a spatial region between a footrest and a brake pedal provided to the motorcycle.

Methods, systems, and vehicles that control the temperature of a device included in the vehicle are presented herein. The temperature of the device is controlled by ventilating the device with drivetrain air, such as transmission cooling air. In some embodiments, the device is at a greater temperature than the drivetrain air, which cools the device. In other embodiments, the device is at a lesser temperature than the drivetrain air, which heats the device. The drivetrain air is provided to the device through an exhaust duct coupled to the vehicle’s transmission. The drivetrain exhaust air is preferably circulated by the transmission. The transmission may be a continuously variable transmission. The device may be an oxygen sensor that is coupled to an engine exhaust pipe. The oxygen sensor is thermally coupled to the engine exhaust and the engine exhaust pipe, which are at greater temperatures than the transmission exhaust air.

A saddle riding vehicle includes a body frame, an exhaust pipe, a muffler, and a catalyst. The body frame includes a main frame, a seat frame that extends rearward from the main frame and supports a seat for occupant, and a rear frame that extends from the main frame upward to a rear and is connected to the seat frame. The exhaust pipe extends rearward of the vehicle from an exhaust port of an engine. The muffler is connected to a rear end portion of the exhaust pipe. The catalyst is disposed in the muffler. An air cleaner box is disposed rearward of the engine. The catalyst disposed in the muffler is disposed in a space surrounded by the main frame, the seat frame, and the rear frame and overlaps with the air cleaner box as viewed in a side view of the vehicle.

An engine includes: an engine main body including a plurality of cylinders; a plurality of exhaust pipes connected to exhaust sides of the plurality of cylinders; a plurality of throttle valves positioned on intake sides of the plurality of cylinders; a catalyst device connected to the plurality of exhaust pipes; and a controller configured to control opening and/or closing operations of the plurality of throttle valves. One of the exhaust pipes is formed shorter than other exhaust pipe. And the controller opens one of the throttle valves upstream of the one of the exhaust pipes at a higher speed or a larger opening degree than other throttle valve upstream of the other exhaust pipe when the engine is started.

There is provided a motorcycle which includes an engine including an exhaust port; an exhaust pipe connected to the exhaust port of the engine; and a catalyst disposed within the exhaust pipe. The exhaust pipe includes a catalyst case accommodating the catalyst, and a pipe connecting the exhaust port of the engine and the catalyst case. The catalyst is disposed in front of the engine. An occupied area of the catalyst in a direction orthogonal to a flow direction of exhaust gas is larger than an opening area of the pipe in a direction orthogonal to a flow direction of exhaust gas. A central axis of the catalyst is inclined with respect to a vehicle width direction in a vehicle front view. And the central axis of the catalyst and a center line of the engine in the vehicle width direction intersect at a position overlapping with the catalyst in the vehicle front view.

An exhaust apparatus includes a chamber disposed below an engine, an inlet pipe guiding exhaust gas from an exhaust pipe to the chamber, a tail pipe discharging the exhaust gas from the chamber to an outside, a first partition wall partitioning an inside of the chamber to a pair of left and right spaces, and a second partition wall partitioning one of the left and right spaces to a pair of front and rear spaces. Another of the left and right spaces is a first expansion chamber into which the inlet pipe enters. A rear space of the front and rear spaces is a second expansion chamber disposed downstream of the first expansion chamber. A front space of the front and rear spaces is a third expansion chamber disposed downstream of the second expansion chamber, and the tail pipe enters into the front space.

An exhaust device in which an exhaust passage wraps around from a front side of an engine to a lower side of the engine and extends to a rear side is provided. The exhaust device includes a catalyst configured to purify exhaust gas in the exhaust passage and disposed in front of the engine, and a gas sensor disposed on a wall surface of the exhaust passage at an upstream side than the catalyst. The gas sensor is disposed in front of the engine so as to be directed toward the engine.

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.

There is provided a straddle-type vehicle. An exhaust pipe includes a first portion extending downward from an exhaust port through a region in front of an engine and on one lateral side of a down frame in the left-right direction, a second portion extending upward through a region in front of the engine and on the other lateral side of the down frame in the left-right direction after extending from a downstream side end portion of the first portion to the other lateral side of the down frame in the left-right direction through a region in front of or to the lower front of the down frame. The catalyst device is disposed in a portion of the second portion of the exhaust pipe that is located in front of the engine and on the other lateral side of the down frame in the left-right direction.