Patent ID: 7267094

Claim:
A lubrication system of a vehicle engine, comprising: a crankcase having an upper case coupled to a cylinder barrel forming a cylinder bore and a lower case separably coupled thereto rotatably supporting a crankshaft having an axis in the vehicle width direction; and a cylinder head having ends along an axis of the crankshaft; the cylinder head including a head side oil passage formed at one of the ends of the cylinder head; the lower case including a supply source side oil passage communicating with an oil supply source and extending substantially parallel to the axis of the crankshaft, and a branched oil passage guiding oil to the head side oil passage and branching and extending upwardly from the supply source side oil passage, the upper case including an upper case side oil passage at one end thereof, the upper case side oil passage extending substantially parallel to and connecting to the head side oil passage in the cylinder head, and a communication passage communicating between an upper end of the branched oil passage provided in the lower case and the upper case side oil passage provided in the upper case, the communication passage extending along the axis of the crankshaft, wherein a lower end of the upper case side oil passage is formed between coupled surfaces of the upper case and the lower case.