Patent ID: 7600500

Claim:
A lubricating system for an internal combustion engine, comprising: an oil tank provided in an engine body having a crankcase which rotatably bears a crankshaft fitted with a centrifugal clutch at one end portion thereof and which defines a crank chamber; a feed pump for supplying oil in said oil tank to a portion to be supplied with the oil of said engine body; and a scavenging pump for returning the oil collecting in a bottom portion of said crank chamber into said oil tank; wherein said oil tank is provided in said engine body adjacent, in the direction along the axis of said crankshaft, to said centrifugal clutch contained in a clutch containing chamber communicating with the inside of said crank chamber; a wall portion partitioning the inside of said oil tank and said clutch containing chamber from each other is provided with an opening portion for communication between said clutch containing chamber and the inside of said oil tank; and said opening portion is located on the outer side relative to the outermost rotational locus of said centrifugal clutch as viewed in the direction along the axis of said crankshaft, wherein said oil tank includes a crankcase cover joined to said crankcase in a manner for defining said clutch containing chamber between the oil tank and said crankcase and a tank cover joined to said crankcase cover, and a return hole, for returning into said oil tank the oil discharged from an oil pressure control unit attached to said crankcase cover at a portion corresponding to an upper side of said oil tank, is provided in said crankcase cover so as to communicate with the inside of said oil tank, wherein said crankcase cover includes a rib that is integral therewith and projects therefrom for leading to said return hole the oil discharged from said oil pressure control unit attached to said crankcase cover.