K1100RS front brake not releasing

[KCinSB]

Bike has been outside, under a Dowco, showing some rust on the ABS tooth ring, not related to the issue. Planned to take it out, pushed off the center stand, and then could not move it. Took the car. Got back and could push it around until 1st front brake use, no release again. With front off the ground, I can see that both calipers are holding on the disc.
  Is it more likely the front brake master cylinder is not allowing return-OR-both caliper pistons are sticking in the bore?

[Laitch]

To me it's more likely a master cylinder problem. When did you flush the system last?

[The Mighty Gryphon]

I'm inclined to think that if the bike has original brake hoses, that the lining is collapsing and trapping the brake fluid in the calipers and slowly letting it out.  This would not be the first time someone has had that problem, and definitely won't be the last. 

[KCinSB]

Guess I should have mentioned Galfer SS lines. Hope they don’t do that also! I expect they use Teflon inner line.

[KCinSB]

I'm inclined to think that if the bike has original brake hoses, that the lining is collapsing and trapping the brake fluid in the calipers and slowly letting it out.  This would not be the first time someone has had that problem, and definitely won't be the last.

I was wrong! Likely will not be the last time either. Only thinking about the brake lines at the rear ABS and at the front and rear calipers! I spaced on the hose at the handlebar front brake master cylinder. It is still the OEM original 30 year old part! While trouble shooting the front brake lock-up, it has started leaking, and quite badly, at the lever banjo fitting. Made a mess.
  SO, please help me find any previous posts here on the subject. Does the Blockage occur in the hose, or farther down line like in the ABS unit? Getting a new flex line installed will be a PITA for access, as photos show. Does a SS P/N 34 32 2 320 214 replacement exist? At the Hose/Hard line junction, is that plastic clamp (not as parts book shows) held down with a bolt and NUT? Was hoping the bolt is threaded into the frame.  Sorry,…. So many questions!

[frankenduck]

Usually replacing the hose will fix it.

I get my SS lines from Motobins. Only takes about a week.

[frankenduck]

For ABS I that plastic clamp just holds the lines parallel, does not attach to anything.

[frankenduck]

Part # is 34322311323.  34322320214 is for a K1100LT with taller handlebars.

[Laitch]

Clamp.

[KCinSB]

Thanks on the P/N and clamp verification!   Now expecting P/N ….311 323 to be correct, and hope a SS is available.
Had just sent off 2 emails to suppliers after hours, A&S and BOMBARS, as I am concerned about the date confusion I have run in to before:

For 1993* K1100RS
Mfr date : 12/92
Vin: WB1053204 P6495632

Hello, wish to find a Stainless brake line to replace the OEM hose, at the front brake handlebar master cylinder. Line runs from the MC to the hardline junction under the tank. My bike is at the year of change and I have seen 2 part numbers referenced:
32 34 2 320 214
32 34 2 311 323 (To 7/93) *

Can you verify which part number is correct?
Do you stock that part? Is it available in SS?

[Laitch]

For 1993* K1100RS
Mfr date : 12/92
Vin: WB1053204 P6495632
My bike is at the year of change and I have seen 2 part numbers referenced:
32 34 2 320 21432 34 2 311 323 (To 7/93) *

The part number that ends in 214 belongs in a K1100LT and I could only find it in the K1100LT ABS I Front Brake Line section of the LT parts fiche.  Your bike isn't at a year change as far as Max BMW"s parts fiche is concerned. It belongs in the (To 7/93) category of the K1100RS section's ABS I Front Brake Line section of the RS parts list where I found it. The K1100 series was introduced in 11/92 so it really hadn't been rolling long enough for BMW to start modifying it, but it only took them a few months or so to start tinkering in earnest. 

[KCinSB]

Yup! Mighty Gryphon, “I'm inclined to think that if the bike has original brake hoses, that the lining is collapsing and trapping the brake fluid in the calipers and slowly letting it out.  This would not be the first time someone has had that problem, and definitely won't be the last.”

Looks like you hit the nail on the Head! After replacing the OEM limp Brembo hose from the handlebar Master Cylinder to the hard line junction under the tank & wiring mess, the front rotor will release as it should. Now I just need to reassemble the motorcycle and try it on the road!

[Laitch]

 

[The Mighty Gryphon]

Great!  Thanks for the feedback.

[sooprvylyn]

i quick fix might be loosening the set screw under the plastic cover on the master cylinder housing.  There is a big screw operated with a large flat head screwdriver on the lever that depresses the maser cylinder piston....unscrew that like half a turn and see if that allows you to at least move the bike.

I wouldnt call this a road worthy fix on a bike with a brake issue.  Definitely flush the system at the least, and probably time to replace them lines.  This is only a quick "fix" to be able to move a bike around in a shop setting.  Wont work if the problem is in your caliper pistons.