oil on spark plug threads

I recently bought a 1998 VFR800 with about 33K miles. I changed the spark plugs today and when I took out the old spark plugs there was oil on 3 out of 4 of the spark plugs. The oil was only on the bottom half of the threads (closest to the middle of the plug), not on the electrode or on the insulator. The electrodes looked like they had pretty normal wear. Would this have come from the person before me putting oil on the threads to keep the threads from locking up or is there some sort of leak inside my engine? The bike runs well and I do not notice any smoke. Your help is greatly appreciated.

 

That sounds like a logical conclusion. Were the threads closest to the combustion chamber a bit sooty and black, or clean?

Regardless, if you aren't using any oil, I wouldn't worry about it too much. There is no telling what the person before you did.

 

The electrodes look pretty clean. I am worried that there is a gasket that is compromised in my engine that is allowing oil to leak to that location.

 

Maybe Dizzy is about somewhere. He deals with this sort of thing all of the time. All I can think of is the valve cover gaskets leaking slightly, but the oil should not be able to get past the crush washer on the spark plugs, unless some accumulated oil got on the threads as you were unscrewing the spark plugs. Can you see if there is any oil in the spark plug wells?

 

The oil did not get past the washer. When I pulled out the plugs, the oil was between the washer and the electrode, on the threads. Now that I have the new plugs in, I don't really want to pull them out again. Do you think I should look into replacing the valve cover gasket. The bike does have almost 33K miles. Is that a big job?

 

Pull the plugs after 10 miles riding and check them again.

Base your conclusions on engine tune from frequent plug checks until it's running as well as it can.

 

Hey Lgn001... It's pretty normal to see carbon/oil residue on spark plug threads. I wouldn't worry about it if all else seems in place.

If even a small amount of oil makes it's way into the combustion chamber, you'll know it when you start your bike by the "fog".

It is possible for oil to leak into the spark plug cavity past the valve cover gasket...however on Hondas where this is possible, there's always a drain hole that comes out usually near the exhaust. It's not impossible for this hole to be clogged, in which case you'd have oil filling up that cavity, which would be abvious when you pulled the resistor caps off. That's my two cents.

 

I just replaced my plugs and I got the same thing, a little bit of black stuff on the threads that may or may not be engine oil. No functionality issues, so I'm not worrying about it until I have a better reason to. :unsure:

Azamat