K11 Owners Group

Off the grid

Which is it?

Sticky internal caliper?

Outer hinge pin that can be lubed?

Front brakes need a bleed?

Front brakes were rebuilt 10k ago, pads, fluid and bleed 5k ago.

Question

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BMGraeme · Posted: Sat Jun 21, 2008 5:08 am Post subject:

With mine it's always been a build up of crud which prevents the piston in the M/C fully returning. I now clean it up every year.
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chopper_harris · Posted: Sat Jun 21, 2008 6:38 am Post subject:

From a mechanical perspective, it is only the spring inside the master cylinder which returns the piston to the rest position.

On the Magura K11 front m/cyl, the spring is appx 40mm long and 8m diam.
It does not take much friction in the mechanical parts to overcome the strength of the spring.

My guess would simply be crud build up between the lever and the housing. Did you refit the front shroud, this should protect the pivot and m/cyl from water and dirt ingress (Bottom left in diagram).

Easy to strip, the pivt pin is a hex socket head bolt, attacked from underneath (Centre of diagram).

Check that the piston boot (through which the actuating arm passes) is intact.

Gently push the piston with a small screwdriver, and test that it travels smoothly in the bore. It is limited on the return stroke by the lockpin (4) in the diagram. If you wish to check the bore and seals, release the lockpin and the piston will eject under pressure of the return spring.

Apply light smear of lithium LM grease, and reassemble.

Do not tighten the pivot pin too much, or it WILL bind the lever. The pivot pin was originally locktited, you may wish to do this, or a blob of paint onto the m/cyl body will indicate any movement of the pin.

A sticky caliper will result in significant effort required to spin the wheel when on the mainstand, and a hot rotor even after minimal brake use.

Good Luck
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Flying Duck · Posted: Sat Jun 21, 2008 7:40 am Post subject:

MY RS has a sticky lever when I bought it. Lubing the pivot pin cured that. And, as noted above, not overtightening it when putting it back in.

The pivot pin is a bit stubborn to get out. You need to get the tip of the Allen wrench as deep into the head as possilbe then put some angular force on it while pulling it out. Not sure if that makes sense. It's hard to explain in words.
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Off the grid · Posted: Sat Jun 21, 2008 11:42 am Post subject:

Thanks for the help guys, especially Chopper.

Mystic Red · Posted: Sat Jun 21, 2008 6:48 pm Post subject:

OTG, I had the same problem and the brake light would sometimes stay on. So with the knowledge provided in this thread out to shop I went.

Loosened the bolt/pin on the bottom and used a screw driver to work it down until I could get a pair of needle noses on it to slide it the rest of the way out. The pin has a plastic sleeve around it so I popped ti off and cleaned the inside of the sleeve and the outside of the pin. Then I cleaned the hole it came out of by shooting it with panther piss (WD40) and working a rag into it with a screwdriver and twisting. I did this until the rag came out clean.
Then I lubed pin, put sleeve back on and reinstalled.

This when things went to $h!t. Pulled brake lever to check my handiwork and the brake light stayed on. What the hell. Pulled it again (stupid,stupid,stupid) and little metal thingy that activates the brake light switch pings off into the bowels of the LT. Can't see it. Magnetic probe hoping it was ferrous (it's NOT). Starting to get pissed. Grab the air hose and put the nozzle on it and blow down into bowels. There it is and it pops out on the floor.
Now here's where I get real stupid. I'm putting metal thingy back in and drop it into the bowels again. SON OF A BITCH. Can't blow it out with air this time. Off comes side panels, seat and tank. Continue blowing and no love. Now I'm REALLY pissed an sweats dripping off the end of my nose. Drop a couple of loud F-Bombs. After about 10 minutes of continuous blowing I finally see it laying on the floor. Put towel where gas tank used to be under the brake lever. Reinstall metal thingy, (after bending it so it will stay on) brake lever and pin. Still sticky.
So apart it comes again but this time I cleaned all grease off pin and sleeve and polished pin with a wire brush on the grinding wheel till it is smoooth. Reinstalled it and now the lever practically snaps back into place.
If you haven't done this yet I hope this helps. I tightened the pin pretty snug and used blue loctite on the treads. Completely clean is the trick that worked for me.
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hockeyshifter · Posted: Sun Jun 22, 2008 1:45 pm Post subject:

well if i can LOL mystic red i can feel you pain.

this is what i know..
it is known that the orignal return spring was an issue and it was too weak for the long haul. any overhaul at the bmw shop installed a new one and the assembly line made changes also..

i have also learned that the m/c assembly contained metal parts from different portion of the periodic table ie: AI Mg Fe and when you add water you get a problem know as galvanic corrosion.
this corrosion can cause the sticking you have now. fix by R& R and coat exposed parts with a anti seize compound.

last .. i know of the seals or cups inverting or fliping in the cyclinder i have been told that the cups can tear and brake fluid can build up between the seals and the dust cap..
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