Do something sooner, rather than later! As the fluid is heading up the pushrod to the clutch assembly (if it does not have the felt washer)!!!
Before I did anything Else I would open the gearbox filler plug and verify the levels?? There is a Small dipstick in the tool kit that it should be filled to not the full depth (I have seen a couple!!!)
Edit Early ones had the Shock spanner with the line on it and the later ones got the small L shaped dipstick basically max is 115mm below the top of the fill port
Fill it back up to the dipstick level with Heavier weight oil 85W140 GL5 drop the boot off (Carefull! it is likely half full in there!) and scoosh out that area with brake cleaner as that looks like pretty thin pish leaking out? Maybe even a low viscosity fully synth!!
#NotAnOilWar
but I have seen many people using fully synth in older bikes with older seals and developing leaks a thousand miles later! When asked I just tell them drain down the oil overnight and refill with the appropriate mineral of the correct viscosity and volume, It appears that that the fully synth can find it way past older seals All of them sealed up with the original oils again People are far too precious of the "oil" The appropriate volume of the correct grade and monitored and topped up, is all that it needs!! Except BMW dry plate transmissions It HAS to be GL5 spec Not a hybrid GL4/5
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Anyway if the above does not fix it? Its time consuming but can be sorted fairly easily, At least with the Chair you can jack it up and get an axle stand or two under it,
Drain gearbox, Remove the rear wheel / brake / swingarm and stuff and that that will let you have a clear look/ work at it (Just hang the calliper up off the rear rails don;t disconnect the brake line and be careful with the speed sensor wiring just unplug and snip the thousand cable ties )
Important! Order a Boot and a Clamp The one you have will likely be like jelly at this stage and likely the clamp will be seized despite all the gear oil
BMW parts K569 (K 75, K 75 C, K 75 S, K 75 RT) K 75 C (0564,0574) Clutch control
www.realoem.com
Order a seal as well Shaft seal 9X15X4
BMW parts K589 (K100, RS, RT, LT) K 100 RS 83 (0502,0503,0513) 5 speed transmission-drive shaft
www.realoem.com
and a can of brake cleaner to get that all washed down
Now I can't remember exactly the rear of an older K gearbox, but Small drill Smaller self tappers Drill closer to outer diameter spray off debris and screw in self tappers and pull / lever and hopefully the seal will pop out for you ! I had bother on a very corroded one (the boot spilt and let is salt and schite) and had to use an old pair of Mercedes dash pulling tools
Clean it all out well
I got a nylon bush made that fits in the orifice and allows me to
tap the seal in to the correct depth*** keeping it half square you might manage with a socket that is as close as possible to the outer seal diameter without being bigger as it will bind and mess you up!
***check depth before removing
Reassemble Cleaning and Lubricating as you go If you want to do the output seal and swingarm gaiter this is the time!
Like I say it’s okay but time consuming and the seal is fiddly Just do your best not to damage the sealing surface on the shaft where the seal runs !!
