Lubricating system in a 4-cycle engine

A system for lubricating a 4-cycle engine, comprising:

• an oil reservoir chamber which stores a lubricating oil therein and has an oil mist producing means contained therein for producing an oil mist from the lubricating oil;
• a crank chamber having a crank portion of a crankshaft contained therein;
• and
• a valve-operating chamber having a valve-operating device contained therein, said oil reservoir chamber, said crank chamber and said valve-operating chamber being provided in an engine body, said oil reservoir chamber and said crank chamber being in communication with each other through a through-hole above an oil level in said oil reservoir chamber, said crank chamber and said valve-operating chamber being in communication with each other through a control valve which is opened upon rising of the pressure in said crank chamber and closed upon reduction of the pressure in said crank chamber, said valve-operating chamber being substantially in communication at its upper portion with the atmosphere and at its bottom portion with said oil reservoir chamber through an orifice, and the following expression is established during operation of the engine:
• Pc.ltoreq.Po<Pv
• wherein Pc is a pressure in the crank chamber;
• Po is a pressure in the oil reservoir chamber;
• and Pv is a pressure in the valve operating chamber.