A snowmobile comprised of a frame having a centerline in a front to rear direction, an engine supported by the frame, the engine having a body defining at least one combustion chamber and having a crankshaft extending generally perpendicular to the centerline and arranged to drive a snow-engaging drive member is disclosed. The engine of the snowmobile has an exhaust system including an exhaust passage extending through the body from the combustion chamber, an exhaust pipe leading from the exhaust passage along a first side of the engine, a valve member movably mounted with respect to the body for controlling the timing of the flow of exhaust through the passage, and a drive for moving the valve, the drive including a motor positioned on an opposite side of the centerline of the snowmobile from the exhaust pipe.