The invention relates to an internal-combustion engine, in particular for a motorcycle. The motorcycle engine preferably includes a crankshaft rotatable about an axis, a web coupled to the crankshaft, and curved wall portions surrounding the crankshaft. The web has an outer surface which defines a substantially circular pathway as it rotates about the axis. Oil is preferably flung from the web and the crankshaft into an oil channel which has a longitudinal axis that is substantially tangential to an adjacent portion of the pathway. Additionally, oil which is flung from the web and the crankshaft onto the curved wall portions drains into the oil channel, which leads to an oil-storage tank. Preferably, the housing also includes a balancing shaft with a balancing web rotatable about a second axis, additional curved wall portions surrounding the balancing shaft and the balancing web, and a second oil channel. The balancing web has a balancing web outer surface that rotates along a substantially circular pathway. The second oil channel has a longitudinal axis that is substantially tangential to an adjacent portion of the second pathway. Oil thrown from the balancing shaft is flung into a second oil channel, which leads to the oil-storage tank.