Oil Leak

[Anonymous]

I just bought a 1980 GS850G in mint condition, or so I thought. It has started to leak oil from what appears to be the air filter. I know this is impossible but it appears to all the world that that is where the oil is coming from. It only leaks when running. Any ideas?

[Jeff Tate]

There should be a breather hose that goes from the valve cover to the air filter box. Some oil collecting in the air box I would assume to be normal unless it's really alot and making a mess. Is your oil level correct and not overfilled?

[bwringer]

Don't take this the wrong way, but are you checking the oil correctly? With the bike on the centerstand on level ground, oil level should be in the middle of the sight glass on the right side. It's happened before that someone thought the bike was supposed to be on the side stand, leading to massive overfilling.

A long time ago, I was guilty of overfilling a GS400 -- it was a little dark, and the new oil was very clear. Somehow, I never saw the surface of the oil in the window as I was filling it.

If the oil isn't overfilled, it might be excess blowby from bad rings. They'd have to be really awful to push that much crud into the airbox, though. It probably wouldn't run very well in that condition. I'd still check the compression.

It could be as simple as the airbox has never really been cleaned out. Some oil in the airbox is normal, since it's constantly sucking in oily mist from the breather. If the bike was just cleaned up externally for sale, you could be getting an overflow of crud. Or maybe some water and/or soap got in there and has loosened up some of the normal buildup of crud.

Let's see, what else...?
A leaky petcock could theoretically dump gas into the engine, causing the overfilling situation, as well as adding a solvent to dissolve more goop.

Maybe you or the previous owner got a little oil-happy when oiling the foam filter, and the excess is dripping out?

Maybe you're mistaking the source of the oil? There's always a small amount of oil coming from the cam chain tensioner on these bikes.

Maybe the airbox just needs cleaning. Make sure you seal it up well if you open it -- some good weatherstripping in the end covers helps make sure it doesn't run lean. GS850s hate to run lean. They actually like breathing through that little snorkel.

Maybe you just went for a ride in the rain or washed the bike, and maybe some water and/or soap made its way into the airbox, and maybe it combined with the normal ick in there and is making a mess as it runs out.

That's about all the ideas I have.

[bwringer]

Two more:

There are little swatches of this course steel wool material under the breather cover at the very top of the engine. These are meant to give oil droplets in the crankcase air a place to coalesce and run back into the engine before the air goes through the breather hose into the airbox. Maybe these are missing.

Maybe the breather hose has come off the airbox (or been accidentally left off, or maybe the hose split), allowing oily vapors to run down the side of the airbox and create the inconvenient mess.

OK, now that's it. I think.