Quite a bit of oil will be ejected from the crankcase vent, that is why it is a good idea to put a line on it and get it outside the cowl. This is also where you inject any afterrun oil in a 4 stroke. Putting after run oil in the carb or exhaust does little good on a 4 stroke. You need to get the oil into the crankcase where it will coat the bearings on the crankshaft.