US Patent 6935297 Lubricating system for 4-cycle engine

A lubricating system for a 4-cycle engine reduces overall engine size and number of parts, and simplifies engine structure. The engine includes a side cover bonded to the crankcase defining a first valve-operating chamber, and a head cover bonded to the cylinder block defining a second valve-operating chamber. Oil reservoir chambers are formed in the crankcase and the side cover. Oil supply passages are provided in the crankshaft to permit a portion of each oil reservoir chamber below an oil surface therein to communicate with the crank chamber so that the oil passed through the oil supply passages is scattered by rotation of the crankshaft to produce an oil mist. The crank chamber communicates with the first valve-operating chamber through a one-way valve. A recovery bore opens into the second valve-operating chamber for recovering oil and communicates with each of the oil reservoir chambers above the oil surface.