A snowmobile has a two-stroke engine having an electronic reverse function so that a crankshaft can be selectively rotated in forward and reverse rotation directions. A gearbox has a first shaft coupled to a countershaft, a second shaft extending parallel to the first shaft, first transmission gears mounted to the first shaft and second transmission gears mounted to the second shaft. The first transmission gears are in constant mesh with the second transmission gears to form high and low gear pairings. A shifter is operable for selectively operating the gearbox in one of a high gear, a low gear and a neutral gear. The engine is selectively operable in the forward and reverse rotation directions while the gearbox is operated in at least one of the high gear, the low gear and the neutral gear.

A gear transmission (20) includes a plurality of shift gears (36, 37), a plurality of shifters (55, 56) engaged, respectively, with the plurality of shift gears (36, 37), and a shift drum (58) rotatably operated by a stepped speed changing operational tool (66) to operate the plurality of shifters (55, 56), thus being speed-changed in forward three speed stages. The stepped speed changing operational tool (66) is switched to a neutral position, a forward third speed position, a forward second speed position and a forward first speed position in this cited order.

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.

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 gear transmission (20) includes a plurality of shift gears (36, 37), a plurality of shifters (55, 56) engaged, respectively, with the plurality of shift gears (36, 37), and a shift drum (58) rotatably operated by a stepped speed changing operational tool (66) to operate the plurality of shifters (55, 56), thus being speed-changed in forward three speed stages. The stepped speed changing operational tool (66) is switched to a neutral position, a forward third speed position, a forward second speed position and a forward first speed position in this cited order.

A gear transmission (20) includes a plurality of shift gears (36, 37), a plurality of shifters (55, 56) engaged, respectively, with the plurality of shift gears (36, 37), and a shift drum (58) rotatably operated by a stepped speed changing operational tool (66) to operate the plurality of shifters (55, 56), thus being speed-changed in forward three speed stages. The stepped speed changing operational tool (66) is switched to a neutral position, a forward third speed position, a forward second speed position and a forward first speed position in this cited order.

Disclosed is a pulley having: a shaft; a first shroud, called the fixed shroud, mounted so as to be unable to move in translation with respect to the shaft; a second shroud, called the movable shroud, mounted to be driven in rotation by the shaft but is able to move longitudinally with respect to the latter; a mechanism for mechanically controlling the longitudinal movement of the second shroud with respect to the shaft, having: —a first assembly, which is mounted on the shaft and driven in rotation by the latter, —a second assembly, which is mounted on the shaft by way of at least one torsion spring such that the relative angular position of the second assembly with respect to the shaft depends on the torque transmitted by the shaft, and —a device for locking in at least one position between the first assembly and the second assembly.

Disclosed is a pulley having: a shaft; a first shroud, called the fixed shroud, mounted so as to be unable to move in translation with respect to the shaft; a second shroud, called the movable shroud, mounted to be driven in rotation by the shaft but is able to move longitudinally with respect to the latter; a mechanism for mechanically controlling the longitudinal movement of the second shroud with respect to the shaft, having: —a first assembly, which is mounted on the shaft and driven in rotation by the latter, —a second assembly, which is mounted on the shaft by way of at least one torsion spring such that the relative angular position of the second assembly with respect to the shaft depends on the torque transmitted by the shaft, and —a device for locking in at least one position between the first assembly and the second assembly.

Disclosed is a pulley having: a shaft; a first shroud, called the fixed shroud, mounted so as to be unable to move in translation with respect to the shaft; a second shroud, called the movable shroud, mounted to be driven in rotation by the shaft but is able to move longitudinally with respect to the latter; a mechanism for mechanically controlling the longitudinal movement of the second shroud with respect to the shaft, having: —a first assembly, which is mounted on the shaft and driven in rotation by the latter, —a second assembly, which is mounted on the shaft by way of at least one torsion spring such that the relative angular position of the second assembly with respect to the shaft depends on the torque transmitted by the shaft, and—a device for locking in at least one position between the first assembly and the second assembly.

Disclosed is a pulley having: a shaft; a first shroud, called the fixed shroud, mounted so as to be unable to move in translation with respect to the shaft; a second shroud, called the movable shroud, mounted to be driven in rotation by the shaft but is able to move longitudinally with respect to the latter; a mechanism for mechanically controlling the longitudinal movement of the second shroud with respect to the shaft, having: —a first assembly, which is mounted on the shaft and driven in rotation by the latter, —a second assembly, which is mounted on the shaft by way of at least one torsion spring such that the relative angular position of the second assembly with respect to the shaft depends on the torque transmitted by the shaft, and—a device for locking in at least one position between the first assembly and the second assembly.