That Sthil, as I mentioned above, uses a pre-mixed fuel, like a 2-stroke.

On regular model thumpers, the oil passes from the gap on the piston ring, which is bigger than normal to induce that blow-by. It then passes from the crankcase to the front housing and valve train via the inner crankshaft bearing or, when the bearings are sealed, thru a hole on the case or on the crankshaft. It's easy