Clutch bleed and slave cylinder purge.

[carl1957]

I get how to bleed the clutch line, however, My Haynes manual recommends purging the slave cylinder as well, yet has no instruction for doing so. Would anyone care to direct this novice to a link?

[AZBMWRIDER]

The end of the line you need to find, is on the right side, below the seat area .
It's covered in a foam tube about an inch in diameter and 2-3 inches long, easy to miss when looking for it .
I think the fitting at the end has an allen wrench plug in it from the factory, you can get a regular bleeder screw to replace the plug .
Then bleed the hydraulic system as you would a brake system .

[carl1957]

Thanks, AZBMWRIDER. This procedure will purge the slave cylinder as well? This is what I'm not clear on.

[carl1957]

If any one reads this, never having done it before, The bleed screw presses into the ball check before the threads engage, making it very difficult to thread the bleeder into the filler adaptor without stripping the threads. At this point into the procedure, the bleeder screw is threaded into the filler adaptor. It looks straight in, however it is very tight, and I don't want to attempt to get it in further, yet no fluid is coming out. The filler adaptor has flats on two sections, indicating that it can be twisted. Does this then open the filler adaptor so it can be bled? Nowhere have I read a description of this part of the process....

[carl1957]

This is old news to most everyone here, but I'm late joining this crowd. Evidently, the filler adaptor is in two pieces, red loctite in the threads. They are separated using heat. A speed bleeder may then be threaded into lower half of the filler adaptor. Speed bleeders all around guys, I'll order them tomorrow. A steep learning curve indeed.... I love the bike though. I LOVE it!

[billbeemer]

you'd be well served by dropping that slave cylinder and taking a look. most of them are severely gunked, and bleeding doesn't help. it will leak on your clutch and then u will give the dealer $2000 for a complete clutch job. trust me.................

[CycleRob]

I get how to bleed the clutch line, however, My Haynes manual recommends purging the slave cylinder as well, yet has no instruction for doing so.

You then asked for a link that explains how, but other than the tedious, difficult job of removing the slave, the next best way is to EVERY YEAR use the slave piston's full lever actuation travel to pump the old dirty DOT4 fluid out. If you do that every year the fluid does not get too dirty and the slave and MasterCylinder (MC) assembly stays quite clean. Here's how:
1--Attach your container's bleeder hose to the newly installed replacement (label says: BMW 34 21 2 330 310 "stuck / piece") bleeder fitting.
2--Remove the MC cover so you can suction out all the reservoir fluid, then wipe it clean. Be careful you DO NOT move/touch the clutch lever with no fluid in place.
3--Refill the MC reservoir with new DOT4.
4--Pull in the clutch lever (very slowly, every time, for the initial half inch (12mm) so the tiny bleedback hole does not squirt the ceiling) and hold it to the bar grip, with a ratchetting bar clamp if you are alone.
5--Rapidly open the clutch bleeder, then close it when fluid stops running. You do not have to go very tight each time on the bleeder torque, just snug it down lightly.
6--Release the clutch lever. Slowly cycle it twice partially to build up some pumping action.
7--Repeat 4, 5 and 6 at least 10 times, watching that the reservoir level does not get too low.
8--Top off the MC reservoir and cap it, you're done.

The only problem is that cycling the slave piston won't completely clean up a very dirty system and here is a real world explanation that you can understand. Imagine you have a wilderness cabin bathtub full of your very dirty bath water 1 foot deep (30.5cm) and just for comparison purposes, you can only scoop away two 5 gallon buckets full and refill it with those emptied buckets refilled with clean water from the river. It would take probably at least 15 "trips" to the river before the water became clean enough for your wife's turn to take her (cold) bath.

Removing the slave for disassembly and cleaning is equivalent to tipping the filled tub over (inside the cabin?), rinsing it out with a detergent and water, then drying it out before tipping it upright for the clean water refill.

If you decide you have to remove the slave, it is easier after you remove the muffler and rear wheel (OilHeads) and much easier to access if it's a HexHead Boxer (R1200R) where the swingarm does not obstruct clutch slave R&R. Once out in the open, use the above methods about the reservoir cleaning and keeping it full enough. Then release the slave's internal snap ring and the piston should very messily "pop" out into your nitrile gloved hand, held over a drain pan. Note the spring orientation and attachment to the piston. You will immediately need to slightly depress the clutch lever to prevent the reservoir from siphoning itself out. Do NOT use brake clean on the rubber slave piston seal, use new DOT4 fluid and a paper towel. After cleaning off the slave bore, big spring and piston, re-insert the piston all the way in to the back wall stop with the bleeder open, then close the bleeder screw to keep the piston depressed. Immediately release the clutch lever and watch the reservoir fluid level go down as the slave piston spring suctions the fluid into the slave. You can now fully bleed the slave before installing it by keeping the slave's bleeder hose banjo bolt mounting point at the highest point. Two people makes this part easier. When the air is removed by bleeding it you can reinstall the slave into the transmission housing, then see how the clutch lever squeeze feels. Good job!

There you have it. Use the method that applies to how dirty your reservoir fluid is and how often you bleed your clutch. Removing the slave is the best way, but you'll only need to do that about every 3rd yearly piston cycling bleed-out. A really filthy system will also require that the MC itself be taken apart too, but that's another topic.

[carl1957]

Thanks to Cycle Rob! At 11,000 K, the bike is like new, the lines bled, the fluid dark amber, but not muddy. for now, I'll go with Cycle Robs method and not remove the slave.

[carl1957]

This is getting better. I received the speed bleeders. Intending to thread the clutch speed bleeder directly into the clutch vent hose, I heated the filler adaptor to soften the red loctite, and in doing so, the plastic at the end of the vent hose melted, and the filler adaptor/vent hose coupling fell off. Now I need a new vent hose. ($150) Maybe I should load the bike on my truck and take it to the dealer before I do any more harm.

[AZBMWRIDER]

What did you use as a heat source for this ???
Well, mistakes happen sometimes, I don't think you'll find anyone that works on their own vehicles, or fixes anything that hasn't on occasion, caused unintentional collateral damage while performing a repair.
I'm a member of that ' club ' !!!!!

[carl1957]

I used a hand held propane torch to heat the filler adaptor.... got it too hot, can't be too eager. Now, I'm at the point where it seems mandatory to lift the subframe, so the airbox can be removed, thus giving access to the slave cylinder, so the clutch vent hose can be replaced. The dealer will have the vent hose tomorrow, I was hoping that I'd be able to install it when I get my hands on it. However, I am stalled. I'd give a hundred bucks to upload to my brain, the prior experience needed to do this job.
BTW, thanks AZBMWRIDER for lending a bit of sympathy.

[carl1957]

I have the rear subframe propped up, there is enough space to get in there with small torx wrench and swap out the clutch vent hose. The dealer said he'll have it tomorrow. Should be all down hill from here...
I'm intending to leave a speed bleeder in the end of the vent hose, it will thread in where the filler adaptor goes.
The airbox does not come out for this. I didn't realize how "built in" to the subframe the airbox is.

[carl1957]

It took an extra two days for the dealer to get the vent hose. It had the filler adaptor red loctited into the steel hose fitting. I put the hose fitting in the vice, then very carefully, heated the filler adaptor with the smallest flame possible, until the loctite was soft, and I could turn the filler adaptor. The female threads were cleaned with a dental pic, and a speed bleeder threaded into the end of the clutch vent hose. Installation went smoothly, and aside from forgetting to put the air intake extention in the airbox, reassembly of the bike went well.
I be wiser now....

[AZBMWRIDER]

I think you need to rethink your heat source, an electric heat gun, is more than sufficient to get the Loctite softened up so you can remove a fastener .

[CycleRob]

I put the hose fitting in the vice, then very carefully, heated the filler adaptor with the smallest flame possible, until the loctite was soft, and I could turn the filler adaptor.

In the future I recommend a different method, so the line nut and it's threads do not get damaged when the loosening forces are applied. When you put the line nut in the vise the tightening force easily distorts the line nut and it's Aluminum female threads will press tighter against the mating Aluminum male threads. That is normally an easy way to strip both threads as soon as they turn. What saved you, if it did do so completely after a close examination, was a full application of red Loctite on the threads that served as an extreme pressure lubricant. Ideally, with a vulnerable part like an attached rubber and plastic hose you want to keep the hose part cool while you quickly heat the loctite region enough to loosen the fitting BEFORE the heat gets transfered to the hose. You also must use a flare nut wrench, essentially a 6 point box wrench with a missing pie slice opening, allowing you to slip it over the hose and slide it onto the hose end nut. That means the the thin walled Aluminum nut will not be damaged/distorted, like an open end wrench will easily do, when you attempt to loosen an Aluminum hydraulic line nut that is always very tight.
Here is what an experienced mechanic would do when removing the proprietary BMW slave bleeder assembly (AKA "factory bleeder chunk") on the Boxers equipped with it.

--Tightly clamp a ViseGrip (VG) plier at the free end of the bleeder assembly, away from the bleeder line nut. Don't worry about the teeth marks the VG will make, you're not going to need that factory bleeder chunk anymore.
--Place a flare nut wrench on the hose nut so the small offset angle of the wrench head points the handle toward the VG.
--Wrap a 4 layer fist size mass of dripping wet rag around the hose and most of the wrench head on the nut, keeping the VG end up higher so the water does not wet the bleeder chunk.
--Heat the bleeder chunk with a big propane torch wrap-around flame near the flarenut wrench end without actually touching the wrenchhead with the flame . . . for 10 seconds tops. Remove the flame. Be aware of what is beyond the flame so you do not roast any bike parts.
--Wait 15 seconds for the Loctite to soften from the transferred heat.
--Try to loosen the nut. It should come loose.
--Don't forget the bleeder chunk is very hot as you continue to remove the nut with the wrench.

When bleeding the slave be careful you do not use full tightening torque between every lever pump cycle. Use just enough torque to stop the flow, so you do not stress the somewhat soft Aluminum nut's threads.

[carl1957]

Perhaps I'll get a heat gun...