I recently bought a 495 engine off a guy. He had it stored in his garage for years. Every now and then he would squirt some 3 in 1 oil into the cylinder to keep it from rusting. When I got the engine and did a quick look over I found that the engine has never been torn down. I started it after having to flush the engine out with gasoline. After it started it poured out thick heavy white smoke. I shut it down after about 5 minutes of running.
My question is will this oil that the guy put into this cylinder create hot spots in the cylinder or piston creating quicker breakdown of parts if I just let it go. Or should I pull off the top end and clean it up real good removing the oil?
I would think any oil that was in crankcase area would be gone by the time the bike ran 5 minutes. There should be no great damage from the oil residue. I suspect you have a clutchside crank seal sucking in tranny fluid. Crank seals often go bad in bikes that sat around a lot over many years. If gas is good and jetting relatively close it should not smoke a lot.