Internal-combustion engine, in particular for motorcycles

A motorcycle engine, the engine comprising:

• a crankshaft having a first axis of rotation;
• a crankshaft web coupled to the crankshaft for rotation with the crankshaft about the first axis of rotation, the web having an outer surface;
• a balancing shaft having a second axis of rotation;
• a balancing web coupled to the balancing shaft for rotation with the balancing shaft about the second axis of rotation, the balancing web having a balancing web outer surface;
• a first substantially circular pathway defined by the outer surface of the crankshaft web as the crankshaft web rotates with the crankshaft;
• a second substantially circular pathway defined by the outer surface of the balancing web as the balancing web rotates about the balancing shaft;
• and
• a crankcase housing the crankshaft and the balancing shaft, the crankcase having a first oil channel with a first oil channel inlet and a second oil channel with a second oil channel inlet, the first oil channel having a first longitudinal axis that is substantially tangential to an adjacent portion of the first pathway such that oil thrown by the crankshaft web as the crankshaft web rotates is directed into the first oil channel inlet, the second oil channel having a second longitudinal axis that is substantially tangential to an adjacent portion of the second pathway such that oil thrown by the balancing web as the balancing web rotates is directed into the second oil channel inlet.

A method of facilitating the flow of oil from a portion of a crankcase to an oil tank, the crankcase partially defined by a first curved wall portion and a second curved wall portion and having a crankshaft rotating on an axis of rotation, a crankshaft web coupled to the crankshaft for rotation with the crankshaft, the crankshaft web having an outer surface that defines a substantially circular pathway as the crankshaft web rotates with the crankshaft, wherein the crankcase is further defined by a third curved wall portion and a fourth curved wall portion and has a balancing shaft rotating on a second axis of rotation and a balancing web coupled to the balancing shaft for rotation with the balancing shaft, the balancing web having an outer surface that defines a second substantially circular pathway as the balancing shaft rotates, the method comprising:

• providing an oil channel in the crankcase, the oil channel having an inlet defined by the first curved wall portion and the second curved wall portion, and the oil channel being in fluid communication with the oil tank;
• rotating the crankshaft and the crankshaft web about the axis of rotation;
• throwing oil off the crankshaft and the crankshaft web, into the inlet, and into a portion of the oil channel having a longitudinal axis that is substantially tangential to an adjacent portion of the pathway;
• draining the oil in the oil channel into the oil tank;
• providing a second oil channel in the crankcase, the second oil channel having a second oil channel inlet defined by the third curved wall portion and the fourth curved wall portion, the second oil channel being in fluid communication with the oil tank;
• rotating the balancing shaft and the balancing web about the second axis of rotation;
• throwing oil off the balancing shaft and the balancing web into the second oil channel inlet and into a portion of the second oil channel having a longitudinal axis that is substantially tangential to an adjacent portion of the second pathway;
• and
• draining the oil through the second oil channel into the oil tank.