Abstract: An overhead cam motorcycle engine includes a cylinder head, a cam cover coupled to the cylinder head, a sealing gasket, and a substantially rigid insert. The cylinder head includes an aperture that is substantially axially aligned with an engine camshaft axis. The resilient gasket includes a sealing jacket that defines an opening. The gasket is positioned between the cylinder head and the cam cover such that the sealing jacket occupies the aperture. The insert is positioned in the opening in the sealing jacket to seal the cylinder head and cam cover interface.

Abstract: A motorcycle engine capable of being supported within a frame. The engine includes a cylinder head having an upper peripheral edge and a valve cover having an assembled width and a lower peripheral edge substantially corresponding in shape to the upper peripheral edge of the cylinder head. The valve cover includes first and second portions coupled together along an engagement surface that does not extend across the entire assembled width of the valve cover. The second portion is separable from the first portion along the engagement surface to facilitate removal of the first portion from the engine. In one aspect of the invention, the first and second portions are separate castings.

Abstract: An overhead cam motorcycle engine includes a cylinder head, a cam cover coupled to the cylinder head, a sealing gasket, and a substantially rigid insert. The cylinder head includes an aperture that is substantially axially aligned with an engine camshaft axis. The resilient gasket includes a sealing jacket that defines an opening. The gasket is positioned between the cylinder head and the cam cover such that the sealing jacket occupies the aperture. The insert is positioned in the opening in the sealing jacket to seal the cylinder head and cam cover interface.

Abstract: A motorcycle engine capable of being supported within a frame. The engine includes a cylinder head having an upper peripheral edge and a valve cover having an assembled width and a lower peripheral edge substantially corresponding in shape to the upper peripheral edge of the cylinder head. The valve cover includes first and second portions coupled together along an engagement surface that does not extend across the entire assembled width of the valve cover. The second portion is separable from the first portion along the engagement surface to facilitate removal of the first portion from the engine. In one aspect of the invention, the first and second portions are separate castings.

Abstract: A lubrication system for a motorcycle engine includes a camshaft support plate that is separable from an ornamental cam cover. The camshaft support plate at least partially defines a cam chest of the engine. A crankcase defines a crankcase sump and the cam chest defines a cam chest sump. A divider wall is disposed between the crankcase sump and the cam chest sump to prevent oil from draining from one sump into the other. An oil pump is mounted on the camshaft support plate, with a pressure chamber of the oil pump being at least partially defined by the camshaft support plate. The oil pump independently draws oil from the crankcase sump and the cam chest sump through a split-kidney intake assembly. Oil pumped from the sumps is delivered to a reservoir, and is then drawn back out of the reservoir by the oil pump and delivered to components of the engine through a series of oil passages, some of which are defined by the camshaft support plate.

Abstract: A motorcycle engine comprising an engine housing, a crankshaft mounted for rotation within the housing, a camshaft mounted for rotation within the housing, a flexible element (e.g., a chain) coupling the camshaft to the crankshaft, and a tensioner mounted adjacent the flexible element. The tensioner includes a support member, a shoe made of a polyimide polymer (e.g., Vespel), and a biasing member biasing the support member so that the shoe is in contact with the flexible element. The biasing member is made from a wire having a quadrangular (e.g., square) cross section. Preferably, the camshaft is supported by a cam support plate, and the support member is pivotally mounted to the cam support plate.

Abstract: A lubrication system for a motorcycle engine includes a camshaft support plate that is separable from an ornamental cam cover. The camshaft support plate at least partially defines a cam chest of the engine. A crankcase defines a crankcase sump and the cam chest defines a cam chest sump. A divider wall is disposed between the crankcase sump and the cam chest sump to prevent oil from draining from one sump into the other. An oil pump is mounted on the camshaft support plate, with a pressure chamber of the oil pump being at least partially defined by the camshaft support plate. The oil pump independently draws oil from the crankcase sump and the cam chest sump through a split-kidney intake assembly. Oil pumped from the sumps is delivered to a reservoir, and is then drawn back out of the reservoir by the oil pump and delivered to components of the engine through a series of oil passages, some of which are defined by the camshaft support plate.

Abstract: A motorcycle engine having a pair of cylinders, a piston disposed in each-cylinder, rotatably mounted flywheels, a crank pin mounted on the flywheels, and a connecting rod assembly for coupling the crank pin to the pistons. The connecting rod assembly includes a master connecting rod having a connecting rod portion connected at one end to one of the pistons and a base portion at its other end. A cap is removably mounted on the base portion and defines with the base portion a coupling for receiving the crank pin. A split bushing is disposed between the coupling and the crank pin. The connecting rod assembly also includes a slave connecting rod connected at one end to the other piston. An aperture is formed in the base portion, a second bushing is disposed in the aperture and a pin is disposed in the second bushing. The other end of the slave connecting rod is pivotally mounted on the pin.

Abstract: An internal combustion engine is provided with a mechanism to release engine compression at low speeds thereby facilitating starting of the engine. The engine has an exhaust valve which is operated by a valve lifter following a cam surface. A cam pin is positioned within a seat in that cam surface in a manner which allows the pin to rotate. A drive member is attached to the cam pin and has gear teeth in a peripheral edge. A flyweight has teeth which engage the gear teeth of the drive member and cause a rotation of the cam pin in response to engine speed. At relatively low engine speeds an eccentric portion of the cam pin extends above the cam surface so as to engage the valve lifter producing an opening of the exhaust valve during the compression portion of the engine cycle. At higher engine speeds the cam pin is rotated so that the eccentric portion of the cam pin no longer extends above the cam surface so that the exhaust valve is not opened during the engine compression.