I just bought a 2000 Ninja 500 and I was giving it a quick tune-up before I rode it. I just set the valves and took out a spark plug to go buy new ones, and I noticed that the threads of the plug had oil on them. Is this normal? I'm definitely looking for problems on this bike because it's used, so I can't remember if I've ever seen oil on the threads before. I DID just set the valves, and the spark plugs are sunk down into wells below the valves, so I thought some oil might have leaked down into there, is this possible? I also thought that since I left the plugs in when I was flipping the cams some oil might have been still on the cylinders or something and splashed up...


My question is this... What else could this be? I can't think of any problem that would put oil on the threads, so I assume it's either nothing or something terribly major. Has anyone else seen this, and what might cause it?
thanks