One plug fouled with oil

[gorrbert]

83 GS1100GL: what I thought was a rich mixture is actually oil on one plug (no 4). The engine was recently rebuilt. New pistons and rings. The engine is low mileage (25k). This bike was stolen and sat for a time. When I got it back the carbs had to be cleaned. I took off the head had it machined flat and kept it inside. I wrapped up the engine well but over one winter it rusted. That’s why a rebuild was necessary. Before it was stolen it was perfect. I think that the dealer who rebuilt the engine may have made a mistake. I never had oil on any plug until now. Thanks in advance for any advice. Gord.

[tejasmud]

I would be inclined to do a compression and leak down test to see what you get.

[BassCliff]

Hi,

Sorry to hear about all the trouble with your bike. Could you have a leaky valve seal?


Thank you for your indulgence,

BassCliff

[80GS1000]

Is the engine smoking out of the breather on the valve cover or the tailpipe?

May be a stuck oil ring from it sitting - try soaking overnight the offending piston with a couple ounces of Marvel Mystery Oil/Seafoam through the spark plug hole on the offending cylinder. Then pull the plug wires and turn the motor over the next day with a rag over the spark plug hole where you put your mystery elixir to keep from spraying MMO/Seafoam all over the place. Install your spark plug, spark plug wires, and go rag the hell out the bike....lots of throttle on accel and lots of engine braking on decel. That should unstick the ring if that's the issue.

[Richsuz]

I got a similar situation, with smoke coming out when cold out of the right muffler. What other possible scenarios can you offer? Are we talking about bad rings? Bad valves? Mine has not been rebuilt. 34K miles. 1 to 3 cylinders are perfect tan plugs. 4 gets oily after 400 or so miles

[gorrbert]

Last time I started the bike there was so much white smoke out my right pipe that for a second I couln't see the bike! But that was the first time it smoked that much. I'll start it tomorrow and see.

[bwringer]

It's either a stuck ring or a bad valve stem seal.

Neither is a disaster. Use the tips above and ride the snot out of the bike for a while before coming to any drastic conclusions. Carry a spare plug or two.

The valve stem seal can be replaced without removing the head. If the bore or rings are badly damaged, you'll find that the problem doesn't get any better, and it'll be time for new rings. Or decide to live with it for a while and enjoy the drop in the local mosquito population.

[gorrbert]

I can do a compression test but not a leak down. I don't have a leakdown tester. I may have the dealer do a leakdown test.

[gorrbert]

Since new rings were just installed and I kept the head inside for the two years the bike was in limbo, I think the logical fault is a ring. I hope it is so the repair would be free.

[chef1366]

You can actually tell if it is a valve stem oil seal.
Mark the spark plug in between the intake and exhaust. Remove the plug. If the oil seems heavy on either side it's a seal. If it's evenly coated it's the rings.