If you take the engine off and drain out the oil from the rotary valve shaft area, make sure to get the air out of that system when you reinstall the engine and refill this bottle. This is doubly important on an inverted engine. I filled up the system by pouring oil into the bottle end of the lower (on engine) hose. As it fills, it pushes out the air up through the upper hose (on engine). There is also a bleed screw that helps to get the air out in heads up engine. You can't just fill the bottle and think you are good to go. This oil lubes the rotary valve shaft, and the gear on it and on the crankshaft that turns it and the gears wont last long without oil. Then things get quiet. If you are successful in the landing, you can now rebuild your engine. Jim Chuk