Abstract: An exhaust emission control system for an internal combustion engine is disclosed. The system includes a NOx removing device provided in an exhaust system of the engine for removing NOx contained in exhaust gases, and an oxygen concentration sensor provided in the exhaust system. The air-fuel ratio of the air-fuel mixture to be supplied to the engine is changed from a value which is leaner than the stoichiometric ratio to a value which is richer than the stoichiometric ratio. It is determined whether or not a sulfur oxide concentration in the exhaust gases is high according to a transient characteristic of an oxygen concentration detected by the oxygen concentration sensor after the air-fuel ratio is changed.

Abstract: It is the object of the present invention to increase the opening area of an air introducing opening without increasing running resistance. An air introducing opening is made at the front of an upper cowling, and side radiators and front forks are exposed to left and right sides behind the air introducing opening when viewed from the front side. Air guide walls overhanging the air introducing opening from the left and right sides of a nose portion and covering the front portion of the front forks are integrally formed with the cowling to guide running air to the side radiators.

Abstract: To reduce noise caused by exhausted cooling air as well as to maintain a necessary amount of cooling air of a cooling fan. A cooling fan is positioned behind a radiator. A shroud surrounds an impeller coupled to a motor and a rotating shaft. The shroud has an inlet and an outlet in the shape of a bell mouth. The bell mouth shaped inlet has its front edge spaced from the rear surface of the radiator by a clearance D, and forms a space around its front peripheral edge. A space is formed via the space, and opens around the periphery of the shroud. The ratio A:B is 1:3 to 5, preferably approximately 1:4, where A denotes a difference between maximum and minimum diameters of the bell mouth shaped outlet of the shroud, and B notes a length of the shroud.

Abstract: An exhaust emission control system for an internal combustion engine is disclosed. The system includes a NOx removing device provided in an exhaust system of the engine for removing NOx contained in exhaust gases, and an oxygen concentration sensor provided in the exhaust system. The air-fuel ratio of the air-fuel mixture to be supplied to the engine is changed from a value which is leaner than the stoichiometric ratio to a value which is richer than the stoichiometric ratio. It is determined whether or not a sulfur oxide concentration in the exhaust gases is high according to a transient characteristic of an oxygen concentration detected by the oxygen concentration sensor after the air-fuel ratio is changed.

Abstract: A radiator cover for covering the side of a radiator. The inside of the radiator cover forms an expelled air path with air being expelled to the outside of the vehicle from an expelled air port of a side section thereof. An intake path for the flow of fresh air is formed in a longitudinal direction and includes an intake port and a duct. An opening section is formed in part of the duct, the opening section being opened and closed by a louver actuated by an actuation member. Expelled air thereby controllably enters the opening section into the duct and is mixed with fresh air. Thus, fresh air can be effectively temperature controlled. The mixed air is expelled from the duct to the rear of the radiator cover.

Abstract: To reduce noise caused by exhausted cooling air as well as to maintain a necessary amount of cooling air of a cooling fan. A cooling fan is positioned behind a radiator. A shroud surrounds an impeller coupled to a motor and a rotating shaft. The shroud has an inlet and an outlet in the shape of a bell mouth. The bell mouth shaped inlet has its front edge spaced from the rear surface of the radiator by a clearance D, and forms a space around its front peripheral edge. A space is formed via the space, and opens around the periphery of the shroud. The ratio A:B is 1:3 to 5, preferably approximately 1:4, where A denotes a difference between maximum and minimum diameters of the bell mouth shaped outlet of the shroud, and B notes a length of the shroud.

Abstract: To reduce noise caused by exhausted cooling air as well as to maintain a necessary amount of cooling air of a cooling fan. A cooling fan is positioned behind a radiator. A shroud surrounds an impeller coupled to a motor and a rotating shaft. The shroud has an inlet and an outlet in the shape of a bell mouth. The bell mouth shaped inlet has its front edge spaced from the rear surface of the radiator by a clearance D, and forms a space around its front peripheral edge. A space is formed via the space, and opens around the periphery of the shroud. The ratio A:B is 1:3 to 5, preferably approximately 1:4, where A denotes a difference between maximum and minimum diameters of the bell mouth shaped outlet of the shroud, and B notes a length of the shroud.

Abstract: A cooling fan arrangement for a motorcycle having a radiator mounted on a left or right side of a water-cooled engine. The cooling fan is provided between the engine and the side-mounted radiator. The cooling fan arrangement efficiently cools the radiator by blasting cooling air from the engine side to radiator side without degrading the appearance of the motorcycle.

Abstract: Wing portions are used to reinforce ground pressure of a front wheel of a vehicle, such as a motorcycle, in which a center of gravity of the vehicle in a driver riding state is positioned between a front wheel and a rear wheel of the vehicle. The wing portions, each of which is provided in such a manner that an aerodynamic center thereof is positioned forward and downward from the center of gravity of the vehicle, produces down-lift.

Abstract: To increase the surface area of an oil cooler and improve the cooling efficiency of an engine for a motorcycle, dual radiators are mounted on the body frame on both right and left sides of a water-cooled engine. Both radiators are inclined relative to a center line of the motorcycle with the larger space between the top ends thereof than the space between the bottom ends thereof on both sides of the engine. Also, the forward portions of the radiators project forwardly from the front end of the engine. An air-cooled oil cooler is provided at the upper space between both radiators in front of the engine and extends laterally across the width of the engine. Furthermore, a cooling system incorporates the radiator and oil cooler configuration.

Abstract: An oiler cooler surrounding the head pipe of a motorcycle on three side and is fixed thereto. It is positioned vertically between the top bridge and the bottom bridge and laterally between the pair of left and right front fork pipes which are inserted through the top and bottom bridges. Upon turning, the cooler remains stationary relative to the motorcycle main frame.