I disagree with the conclusion here. If the engine ran badly, it could be from old car gas, or maybe some kind of problem that occurred before the airplane was ignored, not necessarily because the airplane sat idle.
My personal experience does not agree with the standard theory that airplanes that sit for long periods of time are always seriously harmed.
When I purchased my first 150, it was 30 years old, and only had 1,100 hours on the engine, never overhauled or topped. During those years it had sat several times for 2 years or longer, with no flying hours at all. It ran fine, compressions good, had a little extra iron in the oil at first but this soon straightened out. During my ownership I also neglected the airplane for more than two years without a single engine start (I had purchased another airplane, and planned to sell the original 150, but just couldn't bring myself to put it on the market.)Then after about 2 and half years I decided to fly the original 150 to Clinton. It needed a new battery and oil change, and ran perfectly ever since, no compression problems, no rough running, just as if it had sat for a day instead of 30 months.
I should note that I live in a low humidity area, and the airplane formerly lived in Saskatchewan, Canada, also a low humidity area. I assume that airplanes from high humidity areas would likely have far more rust in the cylinders, and presumably more problems from sitting idle without some engine preservative oil.
Don't get me wrong, I'm not saying this is a good thing, I just disagree that it is a catastrophe. Another example I can think of is Mike Nass (Clinton airport manager). Mike bought a Cessna 120 that had sat neglected for more than 10 years in Iowa with the tanks full of auto gas. The gas had turned to something resembling varnish. He cleaned out the fuel tanks, changed the oil, and the airplane has been running fine ever since.
