Abstract: An exhaust system for a motorcycle having an engine mounted on a front half of a body frame of the motorcycle includes a plurality of first exhaust pipes extending from exhaust ports of the engine, a collecting section at which the first exhaust pipes are collected, a second exhaust pipe including a substantially straight portion connected to a downstream side of the collecting section and disposed under a crankcase of the engine, an expansion chamber connected to a downstream side of the second exhaust pipe and located under a rear wheel suspension arranged behind the engine, an exhaust outlet disposed on a most downstream portion of the expansion chamber, and an exhaust throttle valve and an exhaust gas sensor disposed on the straight portion of the second exhaust pipe.

Abstract: An exhaust system for a motorcycle having an engine mounted on a front half of a body frame of the motorcycle includes a plurality of first exhaust pipes extending from exhaust ports of the engine, a collecting section at which the first exhaust pipes are collected, a second exhaust pipe including a substantially straight portion connected to a downstream side of the collecting section and disposed under a crankcase of the engine, an expansion chamber connected to a downstream side of the second exhaust pipe and located under a rear wheel suspension arranged behind the engine, an exhaust outlet disposed on a most downstream portion of the expansion chamber, and an exhaust throttle valve and an exhaust gas sensor disposed on the straight portion of the second exhaust pipe.

Abstract: An intake apparatus of an internal combustion engine for a vehicle comprises a duct for taking into a wind during a running of a vehicle, an air cleaner operatively connected to the duct, a fuel supply device for injecting a fuel into an intake air coming from the air cleaner, a movable valve arranged between an outlet port of the duct and an inlet port of the air cleaner, a negative-pressure motor for driving the movable valve, and an electronic control unit for controlling the movable valve. The electronic control unit is connected to an ignition means, and the electronic control unit controls the opening and closing of the movable valve in accordance with a rotational speed of an internal combustion engine, an opening degree of a throttle of the engine and a gear position of the engine as control parameters and carries out a delay angular control of an ignition timing in response to the opening and closing control of the movable valve.