Though the lower end looked almost new when it was opened up (including what appeared to be machining chips), due to mileage, and the failing AOS, there was plenty of oily carbon built up on the pistons. Cleaning it was a challenge. Various hydrocarbon solvents (Chem tool, carb cleaner, brake cleaner, lacquer thinner, etc.) were tried with limited success, the best success came with Chem tool. After doing a load of research a two step process seemed easiest. Buy an empty paint can and soak the piston in Chem tool overnight. After a little scrubbing with a plastic brush only a thin tan build up was left, which turned out to be water soluble. Scrubbing that with a hydrocarbon thinner has very little effect. Some soap and water (wrist pin and rings removed) with a little baking soda cleaned it right up. Rinse the heck out of the bare piston in hot water, dry completely with a lint free towel, Make sure water is out of every crack and crevice. Hit it with WD 40 just to be sure no water is left behind, then soak it with Mobil 1. Or the pistons could just be sent out for cleaning, but where's the fun in that?
