Engine having a centrifugal oil separator

A breather and separator assembly for an engine including a crankcase having a crankcase wall, and having a crankcase pressure within the crankcase, the crankcase wall having a stationary aperture fluidly connected to an air/fuel induction system, a cylinder communicating with the crankcase, a piston coupled for reciprocation in the cylinder between a first position and a second position farther from the crankcase than the first position, wherein movement of the piston from the first position to the second position decreases the crankcase pressure and movement of the piston from the second position to the first position increases the crankcase pressure, and a rotating shaft within the crankcase, the breather and separator assembly separate from the shaft and adapted to be rotatable with the shaft, the breather and separator assembly comprising:

• a first side adapted to face the crankcase wall, the first side having an annular groove adapted to be in fluid flow communication with the aperture during rotation of the rotating shaft, and
• an opposite second side,
• an outer edge between the first and second sides, and
• at least one radial passageway extending in the separator between the annular groove and the outer edge.