85 k100 Oil Leak behind alternator ?

[Atabeach]

Not good. Oil leaking from behind alternator…What are my options ? All cleaned up now but oil seems to appear every couple of days. TIA
Ok UPDATE! Main seal leak…Photo #3. Are these 2 leaks related?

[Laitch]

What are my options ?

The first option is to use a pencil, or slender Phillips screwdriver, as a pointer instead of using your finger; either has less diameter, greater reach and would enhance specificity.

Your alternator's shaft seal might be leaking. That shaft connects with the countershaft that is turned by the crankshaft while the engine is running or while the starter is turning. As the seal wears, the amount will probably increase but not gush, thus eventually requiring Simple—or perhaps Soylent—Green and copious rags for cleanup in time for visitors. If this relic hasn't been ridden much, more riding could possibly stop the leak.

[Atabeach]

Thanks Laitch! The leak appears to be getting worse. It has become my daily driver. Further, someone on MOTOBRICK commented this could be from a main seal leak…I have a leak out of the weephole at the bottom of transmission …can these be related? 😳 I will use a pencil in the future.

[Laitch]

The weep hole drips oil leaking from the engine output shaft O-ring, the rear main seal or from a transmission cover seal—the usual suspects. Transmission fluid smells like sulfur.

[Atabeach]

Ok soooo The alternator leak seems to have stopped. However I do have a leak out of the weep hole. Not sulfur odor so lets assume main seal? ...I'll know more when I get in there....again! ( last time to lube splines )
 Couple of questions...how much of a PIA is the seal removal without the tool? ...and the importance of leaving the new one a little proud?.05mm.
Any input on this procedure would be greatly appreciated.  PS...this barnfind was the only time I used Dino oil in any of my bricks...and stuff leaked. Should I go back to Synthetic Mobil 1 15/50?

[Laitch]

The leak is not necessarily coming from the rear seal; it could be coming from the engine output shaft o-ring. You won't know until you remove the transmission and take a look around the clutch assembly. Main seals tend to leak with more output than shaft o-rings. O-rings might only leak a couple of drops a day if you're lucky.

Some riders would replace both for peace of mind, regardless if only one of those components were leaking. My piece of mind comes from my mind, so that often lessens my cash outlay and saves me time.
 

The projection spec for a new Teflon rear main seal is 0.5mm, not 0.05mm as you seem to believe. There is no requirement for anybody to follow instructions, let alone even believe them. That's the beauty of free will. I have no imagination so I just follow them.
 

[Atabeach]

Thanks Laitch, I am probably going to replace the main seal when I am in there due to the age and since the bike sat unused since  2008. I was going to go with OEM instead of Teflon…thoughts? The installation of the OEM seems easier and more forgiving…and cheaper!

[Laitch]

The Teflon seal migrated to being the OEM starting in 1988 with the GS models. They are now used in various locations in the Brick. Read the details in the link at the bottom of this post. Teflon seals are not greased or oiled before installation. Mounting surfaces must be clean and smooth. All Teflon seals have the stacked rings on their sealing edges. The face of the seal can vary by manufacturer. The photo is from MaxBMW's parts fiche.

As far as installation being "forgiving", the installation of either seal can be botched. All a correct installation of any type needs is understanding and patience.

[Atabeach]

Great info Laitch..Thanks!