MOTORCYCLE ENGINE

摘要

The present invention is directed to a four-stroke engine. The engine is a motorcycle engine and comprises a cylinder and crankcase (216) that is formed as a single casting, and a movable piston (284) received within the cylinder and crankcase. The crankcase defines a first sealed chamber (296) that receives a crankshaft and a connecting rod, and also defines a second sealed chamber (300) that receives a plurality of gears. The engine further includes a first oil in the first chamber and a second oil in the second chamber, where the second oil has different physical properties than the first oil. The engine further includes a crank assembly cartridge (298) that is formed as a removable unit and disposed within the first chamber and a transmission assembly cartridge (302) that is formed as a removable unit and disposed within the second chamber.