Join Date: Jun 2002
Location: The Deep South of Vermont
Rebuild or Replace
Rebuilding would be pretty easy.
Quote: "BTDT I dismantled two and found that the seal sheds little balls of material as it deteriorates. It doesn't take much of a build up of this shedding to create a space for the leak."
This is a very interesting observation, Jeff, thank you for this information.
Quote: "I have a good friend who designs hydraulic systems and he found a replacement that he thought would do better in this environment, brake fluid. I can't find his email right now but have asked him to send me the info again and I will pass it on when I get it."
Jeff,If you do get a substitute part number, please share it with us here.
Now I am thinking that just drilling a weep hole to let leaking fluid out isn't the only thing to do. Proactive change out of the seal with a different (non-BMW parts inventory) seal is a good idea. If you're going to go to all the trouble of drilling the hole put in a different seal.
NO way a seal should be shedding "little balls of material". I wonder if BMW got a bunch of bad clutch slave seals like they got a bunch of bad tire valves. If that is the case then replacing the just the seal or the whole slave assembly might result in putting back in another bad BMW seal. That thought might send me looking for an alternative seal source and rebuilding as long as all the other components check out okay.
I have rebuilt several clutch and brake master and slave cylinders off 1970s vehicles and have never see a seal failure such as Jeff describes. Corrosion of the cylinder, scoring of the seal, etc. I have seen. I have rebuilt several BMW airhead front brake master cylinders using the Original Seals when the seals looked good. These are bikes that have been sitting for decades without brake fluid change, in one case the brake caliber cylinders were seized, and the brake fluid was cloudy mud. Complete disassembly, clean up, and reassembly with the original seal in the master cylinder and it is working fine. If a 1970s BMW can do this, a 2000+ year model should have a clutch cylinder that never needs replacing. Yup, my bet is that some of the seals in K1200LT clutch slaves are of bad composition and that is why they are failing.
Like the tire valve situation, there is no telling how many defective clutch seals and clutch slaves with bad seals are distributed throughout the BMW parts system.
Crown wheel bearings, tire valves, clutch slave seals.... these aren't BMW engineering problems. These are quality contol issues with BMW contract suppliers. (I know that is true with the tire valve situation, I am betting it is the case with the crown wheel bearing, and now I strongly suspect it is the case with the clutch slave seal).
BTW, my 2000 KLT has over 50K miles, no final drive failure, no clutch failure, the tire valves were defective but I disovered before any failure thanks to some posting about the problem. Love the bike and plan on keeping it indefinitely.