Everyone has different standards. Any engine that runs OK is a "good" engine regardless of its internal condidtion. Usually they stay "good" right up until they fail nevermind that the rusty bearing has been grinding itself away for a several of seasons. I have not found one single used glow engine that does not have corrosion pitting on all steel parts. The harder that I look the more corrosion I find. I suppose that the previous owners just chose to stick their head in the sand and say everything is fine and whatever "I" am doing is the correct action.