If you use after run oil, it is also the place you insert it. The only way to get after run oil to where it is needed on a 4 stroke is thru the crankcase vent. If you put it in the carb or exhaust, you only lube the valves, not the main bearings where it is needed. It is kind of tricky getting enough in (you need at least a teaspoon full) but, by connecting a tube to the nipple and rotating the prop while inserting the oil, you can suck it in as the piston approaches top dead center.