Abstract: An overcenter tensioning apparatus is provided including an elongated crank member having a first tension member pivotally anchored thereto at one end, an elongated lever arm pivotally connected thereto adjacent its other end and a second tension member pivotally connected thereto intermediate the first tension member and the lever arm. The crank member, when the remote ends of the tension members extend outward in opposite directions, is swingable in one direction toward a limit position slightly past a center position between respective release and tensioning positions and abutment structure is operatively associated with the lever arm and crank member for releasably limiting angular displacement of the lever arm in opposite directions.

Abstract: A chain sprocket having guide plates comprising flanges of a frangible material located along opposite sides of the sprocket is disclosed teeth and projecting outwardly therefrom to prevent lateral disengagement of the chain under conditions of severe usage, particularly with use of the sprocket and chain assembly on a racing motorcycle. The guide plates are particularly useful in guiding the slack lower reach on of a motorcycle chain during acceleration of a motorcycle, and are also useful in guiding the slack upper reach of the chain during deceleration.