1990 K75 Rear Wheel Lockup

[Fortunato123]

Ok, All back together now. Took it for a ride today. The new MC and rebuilt rear caliper are working very well. I loosened both adjustments under the rear brake pedal to make sure I had a little freeplay in the pedal as Lee had referenced earlier.

Thanks again for all the assistance and Happy New Year!

 

[PGlaves]

Now that the problem is solved let me tell my all time favorite "brake" story. I forget the year but Voni and I had ridden to Sturgis for Bike Week, aka the Black Hills Motor Classic. Main street was as usual congested so we parked our bikes about one and a half blocks away in the outer fringes of a grocery store parking lot. We started walking to Main Street. About a half block later we encountered an appropriately dressed pirate with his bikini clad lady in her high heeled shoes with their motorcycle pulled up on the sidewalk. It smelled "hot" and he was energetically kicking his rear brake caliper while she stood by crying. I asked what the problem was. He said his back brake was locked up. They had just unloaded the bike from the trailer and had only ridden about 6 blocks and the brake was locked up.

I asked him if he had a tool kit and he said yes. He got it off the top of his front fender. It contained a few tools. Most notably it contained a medium size Crescent adjustable wrench, a screw driver, a pair of slip-lock pliers and a claw hammer. I told everybody to stand back and used the Crescent wrench to open the bleed valve on the rear caliper. With a little spurt the volve released some hot brake fluid and the pressure was relieved. I then asked if he had checked or adjusted the brake pedal recently and he said he didn't but his buddy/cousin/brother/somebody had. I checked! There was absolutely no freeplay at the pedal. So using his Crescent wrench and slip-joint pliers I adjusted the pedal so there was some free play so that fluid could actually return to the master cylinder instead of being trapped in the wheel caliper.

His bikini clad lady had by then quit crying and they rode off smiling, as Voni and I walked on to Mainstreet.

 

[pauls1150]

And they didn't even buy you a beer??? Slimy dogs!

 

[98lee]

Ok, All back together now. Took it for a ride today. The new MC and rebuilt rear caliper are working very well. I loosened both adjustments under the rear brake pedal to make sure I had a little freeplay in the pedal as Lee had referenced earlier.

Thanks again for all the assistance and Happy New Year!

Fortunado,

I haven’t had time to try the 16mm master on the back of my bike yet. What is your impression of the 16mm vs the original 13mm master?

Is the pedal travel noticeably less?

Is the needed pedal pressure noticeably heavier? Objectionably so?

 

[AntonLargiader]

One customer with a K1200RS adjusted his rear brake pedal height and then crashed in an intersection when it locked up. Didn't know that you had to compensate with the adjustment at the MC as well.

Another guy with a K12 did something similar and stayed on the gas until the caliper was smoking. The pads were bent, dust cover was melted and the caliper was pink with the seals burnt out and leaking.

The K75-K1100 use the Magura MC with the mounting holes on the top. I know of three different part numbers and they are all NLA. Later bikes use Brembo MCs with the mounting holes underneath. My list has TWENTY THREE of those and I'm sure I don't have all of them listed. Why BMW couldn't just make do with six or eight, I have no idea. Many of them are the same MC but they come with a different length pushrod or the inlet is at a different angle.

I don't know the answer to the K MC issue, other than having them rebuilt by Apple. Rebuild kits for all three show as available.