Originally Posted by PyroMan
First, does this engine need a total break down and cleaning? It's got what appears to be dried fuel residue and the like on the outside of the engine, but when I took the back cover off of the engine to expose the crankshaft and piston assembly, it is very clean in there. ..............
Also, I have some nitro fuel at my house that is 10% nitro and 18% oil. I'm not for sure if the oil is synthetic or castor oil. All the container says (that I could find) was "Lubrication Package by Klotz".
It sounds like you got a good deal. The OS Max is a nice engine; getting a plane with it is just icing on the cake.
From the photos, the engine looks to be very clean. I would not be inclined to disassemble any further at this time. Use a Q-tip to clean any dust or dirt from the carb intake. Plug the carb intake with a piece of paper towel and block the fuel nipple, then give the engine a good brushing with a toothbrush. A little denatured alcohol will help cut the dried oil --- you could use fuel, but it will leave an oily residue that will just attract more dust. Add a drop or two of light oil to the intake and down the glowplug hole, then flip smartly to distribute the oil throughout the engine.
Patriot RC fuel is blended, I believe, by Wildcat Fuels out of Nicholasville, KY. If so, the Klotz package is an 80/20 synthetic/castor mix. 18% oil is a sufficient amount, but you can always raise it slightly by adding castor --- Klotz Benol is the castor component in Wildcat fuel and would by my choice for a castor source.
Before fueling up, be sure to shake the container well to remix any oil that may have settled out.