For the record, this is wrong. It's true for 2 cycle gas engines but the GM two strokes have an air path entirely separate from the crank case. That's what the Roots blower on the side that gives them that distinctive whine does. They also have crankcase breathers that were so famous for filling engine rooms with a fine oil mist that they spawned a whole aftermarket industry.For the record a 2 cycle engine used the crankcase as part of the induction plumbing.