2005 Gravely zero turn with 21 hp Kawasaki motor. Suddenly started an oil leak, dripping when running. Thought it was the lower shaft seal. But, it stopped when sitting overnight. Then figured it must be only when running, and tested that, but no leak. Saw lots of oily, but dry, gunk in cylinder fins, so took off fan shroud. Yikes, totally covered and blocked air flow, but found no liquid oil anywhere on top or in the fins. Maybe a little seepage on upper crankshaft seal? Made a mess, but blew all the crap out, and cleaned it with BrakeClean, now 90% clean. Started it up, no leak. Put it back together clean, and ran it. Runs normally, including mowing, and no oil leaks. Specifically checked lower seal area. What’s the mystery? I’m baffled, but hoping it’s okay.