Oil in my airbox!!

[95PD]

This one ought to be a fun diagnostic...

The bike: 1995 R100GS PD

Started the bike last night, smelled a little oil, and also noticed white puffs of smoke coming from the exhaust when I twisted the throttle. This is new. I got to thinking about it and remembered that the last two times I rode, I smelled burned oil, but wasn't sure if it was my bike or traffic. I've also noticed that in the last month, I've had to add oil to the bike after every 400 mile ride.

This is a new bike to me (2 months) but it only had 14,646 miles on it when I bought it. I changed the oil as soon as I bought it (not the filter though), rode it about 800 miles, then took it to Blue Moon Cycles and had them do the 12,000 mile service just so I could establish a baseline. Since the tune-up I've put 2200 miles on it, and just began noticing the oil smell in the last week.

I got to thinking it might be a ventilation problem so I removed the tank and air filter cover, and low and behold -- there's a small puddle of oil in the air box.

Now, let me back up a minute: after the first week of owning the bike, my Valeo starter locked up, so I changed it out in a matter of a couple of hours (man do those Bovarians know how to build a machine!) At that point I looked into the airbox and there was definitely NO oil in it. So I'm kind of wondering if the problem began after my 12k service??

Here's what I've been able to discern within the airbox:

1) No hoses are crimped inside the airbox or under the starter cover.
2) Oil is inside the airbox
3) Removed the clutch side air intake hose (from airbox to carb) and noticed oil throughout, and a small amount of oil on the outer aperture of the carb (where the hose attaches) but no noticeable amount of oil anywhere inside the carb.
4) Inside the airbox, oil throughout the inner part of the clutch side hose, but none whatsoever on the throttle side hose.
5) No noticeable oil coming from the ERG (?) valves inside the airbox.

At this point, I'm thinking it has to do with the clutch side of the motor since I don't see any hints of oil on the throttle side. I'm wondering if the carbs are out of balance? I can't figure from which direction the oil is coming - from the cylinder to the carb, out of the hose and into the airbox (hard to believe that oil is creeping around the rings with such low mileage)? Or is the metal tube that extends from the airbox to the cylinder head siphoning oil into the airbox then back out of the carb air hose and down into the carb? Again though, I didn't notice any oil from the ERG (?) valve, but I could be wrong. Is there something that the shop does at the 12,000 mile service that might cause this?

At any rate -- I'm at a loss, and the Clymer didn't help too much with troubleshooting. I'm going to call the shop tomorrow and see what they can tell me. In the meantime, I figured I see what kind of input I could get on the boards.

Thanks in advance for your help,

Mike

[PeoriaMac]

Mike,
Somone who has a later bike than mine can tell you properly, but BMW put an oil vent tube (the crankcase breather) into the airbox. On the '78, it aims more toward the right side of the bike. There is a valve there -- a rred valve in your case, I believe.
Anyway, there may be a problem with your valve, or you may be running a little bit more oil in the crank than you need.

Mac

[95PD]

Within my airbox proper there are two vent tubes that go down to each cylinder head. There is another hose coming from the airbox going to through the starter cover, and landing on a cover that is bolted directly above the crankcase -- so it seems that this might be the crankcase vent tube. I will definitely ask the shop if any of these three might cause my problem.

As for too much oil -- my dipstick dead center between min and max.

Thanks for the suggestion,

Mike

[Cosmoline52]

On the older /7's such as my '78 100S that crankcase breather hose is routed to the rightside intake tube. The tube originates from that cover you're referring to which encases the breather valve.

Supposedly BMW began to recognize crankcase pressure problems with the advent of the /6 900's due to relatively small crankcase volume and the bigger slugs. IIRC they opened up the case some with the /7 models and changed the venting system to reduce flatout blowout of the crankcase gases resulting from the even bigger 1000's.

I used to run the heck out my engine in the early days so it was only a matter of a couple years before the blowby started picking up, complete with oil dripping from the right intake tube and a pronounced "hoonking" noise at idle when hot. Turns out the breather valve, a spring loaded fiber disc piece, had eroded severely and my engine had become an oil pump. BMW had an improved all-metal reed valve upgrade by then so I installed it and goodbye blowby problem.

I agree with Mac that your valve may have a problem, I have well over 100k on mine but then again I've never checked it since installation! Maybe my valve is bad and I don't REALLY need that first overbore! ;) I suppose even with your low mileage the valve could be at fault, they're simple in design but stranger things have happened...

The other thing that comes to my mind... is your crankcase overfilled with oil? Beemers don't like that condition and will throw it out everywhere... but once again you seem to have more oil on the right side so my gut says "crankcase breather"...

[lkchris]

There's a hose that runs from the crankcase ventilation breather valve near the top front of the engine (under the cover) to the airbox. Then a plastic connector is pushed into that hose that serves as a "t" to further hoses that distribute crankcase vapors to the air intake tubes.

There can be leakage at the "t" connection if the hose is split at that location. There are also other places for this system to leak.

Nevertheless, with everything in good condition you're still going to get some oil in the bottom of your airbox, in your air tubes, in your carbs, etc. It's normal.

There is no performance improvement to be gained by routing crankcase vapors elsewhere, nor is there any penalty resulting from this system, but there can be an environmental penalty to modifying it. This is the equivalent of "positive crankcase ventilation," pcv.