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1999 K1200RS
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2 Posts
Discussion Starter #1
Dear all, first post.
Yesterday my rear brake locked up. I had to remove brake caliper to get back home. At home I was able to push both pistons back, but not both at the same time. Any ideas?
Fluid is not returning to foot brake piston as there is no resistance anymore when pressing foot brake.
 

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2009 K1300S, 2017 S1000R
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406 Posts
Yes, your rubber hose for the brake has deteriorated and pieces have formed a check valve inside where you can not see any problems. You need to replace the hoses with a new set. But Spiegler hoses on line, better and cheaper. Of course you will need to do a good brake bleed/flush after the lines are installed. A very common problem with old rubber lines.
I don't think this is a master cylinder on your foot lever problem but I don't completely rule it out. Someone else will have opinions too.
 
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Probably hoses as Beech says above, but could be master cylinder. If the plunger isn’t returning all the way out it could block the return. Constant pressure heats brakes, brakes heat fluid, fluid expands & can’t return, adds more pressure, creates more heat, ultimately enough pressure to lock the brakes. Ask me how I know (although this was a truck, not a motorcycle!)
 

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1999 K1200RS
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Discussion Starter #4
Hi, and thanks for your input. Sorry for slow communication. I will try to source Spiegler hoses, the backbone is that I will pay more for shipping and tax than for the product itself. However I disconnected the brake hose at foot brake piston (main foot brake cylinder) and I was able to press pistons back and fluid came out. So new master to be ordered also. Any suggestions for where to order? i am also looking for a replacement of rusty bolts all around and a new seat due to wear. Sargent or?
 

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2009 K1300S, 2017 S1000R
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406 Posts

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If a K1200RS/GT the master cylinder pushrod may be overextended at its adjustment.

If so the brake will stay on and overheat but also the brake fluid won't return to the reservoir.
 

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Rear caliper pin seized on me due to barometric pressure induced moisture ingress.
A bugger to deal with on bike. Had to ebay a new caliper for parts.

Warped rotor as pads would get pushed in but seized pin would not allow float back.
 
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