Internal combustion engine with lubrication system

An internal combustion engine for a vehicle, such as a motorcycle, includes a crankcase defining a sump, and a lubrication system scavenging oil from the crankcase and supplying oil to the crankshaft and to first and second cylinder heads. The lubrication system includes a pump with housing and rotor, the housing being fixed to the crankcase and the rotor being rotatable around a crankshaft axis and being rotated by the crankshaft. A plurality of oil supply passages extend through the crankcase, potentially including at least one being formed in the crankcase.