If you put too much oil in the engine when its rotated it can hydraulic lock and with enough force you could bend something, like the rod. I remove the glow plug and then put lots in the bottom end of the engine. I then rotate it by hand and then rotate it with the electric starter. Watch the oil coming out the glow plug hole!! I usually turn the airplane so the engine is upside down so the oil does not shoot straight up. I then repeat the process at least twice. I then reinstall the glow plug.

If you take the engine apart right after this, you will notice the insides are coated very well and there is not much excess oil, to get in the way the next time you start it up.

I have used in the past air tool oil and now I am using a 50/50 mix of air tool oil and ATF. Seems to work well and smokes less on startup.

Generally, I close the throttle barrel and fill tie top of the venturi with oil, open the barrel, let it drain down the carb and rotate it a few times by hand. If it a larger displacement engine I repeat the process, once I'm sure the engine has enough oil, I bump it with the starter for about 3-4 seconds to distribute the oil into the cylinder. Thats all folks, nothing else needed, just make sure your tank is empty and perform that process and it will survive daily and winter storage for years to come, for cleaning off varnish stains, there are 2 methods of removing them, one is caustic but yields excellent like new finishes, the other is semi toxic but does a good job as well, the caustic proceedure is to buy a foaming alkaline base condenser coil cleaner, available at any HVAC supply house, it will remove almost all varnish and gum deposits and brighten aluminum, the less invasive way is to use regular old engine antifreeze, put the engine parts in a old pot and bring it to a boil, the antifreeze will remove deposits and clean the metals, plus it will protect them from corrosion. The coil cleaner works very good but use it on external surfaces only!, it will etch internal parts, and it is an electrolite, so a chrome,brass and aluminum cylinder will get eaten by the solution, I only spray the outside of the engine and let it sit for a few minutes to clean it up, then rinse it with water. If you let it sit the metal will discolor and the cleaning will have to be redone.

Just thought I'd throw that in there seeing how some people seem to ask how to clean up the engine after the seasons over as well, I perfer the alkaline method but it's hard to handle and perform, that's why I recommend the safer way to everybody who want's to clean the varnish off the engine, just use engine coolant.