Oil Leak Question

[kdannies]

My 1991 K100rs has just developed a leak/seap between the transmission/final drive? housings just behind the cowling that goes underneath the engine. There is a small hole directly under where the transmission/final drive meet where the oil seems to be seeping..nothing major at this point. As I'm mechanically inept I'll be taking it to the dealer for a look. Is this transmission fluid? The engine oil level seems fine. Anyone else run into this issue? The bike only has approx 9k on it and has been virtually trouble free since I've owned it. THe only other possible symtom has been the shifting is becoming a little 'notchy'

[Bobmws]

Does the leaking fluid have a sulphur smell? If so it is gear lube from the transmission. If it appears to be motor oil it is most likely the rear main seal. The notchy shifting is more likely due to the transmission spline being dry and needs to be lubed. Either way the transmission has to come out. At this point replace the rear main seal and both the transmission input and output seals. Not a hard job, but time consuming. Look on the IBMWR.org tech pages for a detailed description.

[deilenberger]

Originally posted by Bobmws
Does the leaking fluid have a sulphur smell? If so it is gear lube from the transmission. If it appears to be motor oil it is most likely the rear main seal. The notchy shifting is more likely due to the transmission spline being dry and needs to be lubed. Either way the transmission has to come out. At this point replace the rear main seal and both the transmission input and output seals. Not a hard job, but time consuming. Look on the IBMWR.org tech pages for a detailed description.

Bob has some good advice.. a few little points:

1. Most K bikes of this age have the slight weep from that hole. It is usually caused by the O ring behind the big nut that holds the clutch housing to the output-shaft drying up and cracking. I have never heard of - or seen - this cause any real problems, and the amount of leakage is so small you won't notice any drop in oil level between oil changes. As Bob pointed out - the engine oil doesn't have the distinctive smell of sulphur that gear oil has, so if it doesn't smell like Hades - it is likely this O ring.

2. Since you're going to have a dealer do the job - in all likelyhood the dealer will want to replace ALL the seals (rear main, O ring, transmission input) - if you feel the mechanics are good - you should let them do it. If not.. well, I'd look for a different dealer.

3. Before going to the dealer for the job - stop at a Honda dealership and buy a tube of Honda Moly-60 (it's used on shaft-drive Hondas.) Ask the mechanic at the dealership to use this on ALL splines (transmission and rear-drive.) It works well and has proven itself on a lot of K bikes that have used it. BMW does have a new lube finally (they dumped #10 - which was awful) - but the new lube doesn't have any track record, so I'd be hesitant to use it.

HTH,