K11 Owners Group

[ridetoday]

I hope someone will endure this lengthy entry and provide some feedback. I apologize for the length, but there might be a clue in here somewhere. By the way, I have had experience rebuilding master cylinders on a K100RT and never had a problem. Same for a few cars I have owned.

The intro: 1996 K1100RS. Complete ABS system removed quite some time ago by a previous owner. I have owned the bike for about 6 months, and have put approximately 5,000 miles on it during that time.
The problem: Brakes were working fine, although fluid for front was somewhat discolored. Front master cylinder began to leak, so a rebuild was in order.
When I removed the sealing sleeve, I noticed some debris, similar to sticky varnish, around the sealing ring of the master cylinder body. Removal of the piston revealed some corrosion in the cylinder, but this was corrected with a proper honing, followed by thorough cleaning. There was also some of the varnish-like debris in the cylinder. During dis-assembly I noticed that the actuator rod was not marked as to proper depth going through the lever and the sealing sleeve.
New piston and seals were installed, and the master cylinder reassembled. I placed the actuator rod at what I thought was about the same depth as previous. New fluid was used to completely flush the system.
There was a bit of a problem bleeding the brakes, but with patience, this was accomplished. Did not see any debris expelled during the bleed process. The front brakes were tested while the bike was still on a jack and the front wheel could be spun.

A test ride was conducted by riding for approximately 30 minutes on roads with varied speeds. I began on a residential road and never exceeded 30 mph for about 5 minutes. Then it was on to higher speed roads with a five minute run at about 60, followed by a slow residential road back to my house. During this ride, the brakes were applied several times with adequate affect. A bit spongy, but nothing that was of concern. Upon completing the ride, I bled the brakes again and did get a bit of air out of the system. The bike sat overnight, approximately 14 hours.

The next morning I left for what was to have been a two-hour ride. The brake lever felt firm, but with the normal amount of play or give one would expect. I left the residential road and was up to 60 on the highway for about 5 minutes. Brakes were applied as I slowed for some small town roads. Again, lever felt normal and brakes worked well. Then it was onto another highway with 60 mph speed. Within 10 minutes (15 to 17 minutes of total ride time – about half of previous day’s ride) of constant 60 mph speed, the bike began to slow although the engine was running okay. As I pulled to the side of the road to determine the problem, I pulled in the clutch to downshift and the bike slowed dramatically! A touch of the front brake lever revealed that it was very solid! There was absolutely no play or give to the lever. In short order, the front brakes completely locked up, but thankfully I was going quite slow by then. The brakes and rotors were quite hot and it was impossible to roll the bike. The rotors and the pads cooled and when they were at ambient temp again, the brake lever was back to a firm feel with a bit of play and I could roll the bike. Not knowing exactly what had taken place, I backed off the actuator rod about a full turn, which gave a bit more play in the lever. I then took slower speed roads back home. No problems getting home, although the pads and rotors were warmer than I would have expected.

My question(s): Did I incorrectly adjust the actuator rod, and if so, how does one determine how to correctly adjust it? The Clymer manual says nothing about this. Or, perhaps in hind-sight, should the calipers have been rebuilt as well? (Thinking here about the debris that was in the cylinder.) The pads are only about ½ worn, so I did not see a need to rebuild the calipers and install new pads.

I am guessing here, but it seems that the pistons did not move back into the calipers and pull the pads away from the rotor once I released the brake lever. This caused excessive heat at the highway speed, which in turn built pressure in the system, causing the pads to clamp the rotors tighter. So, again, did I incorrectly adjust the actuator rod or is there a problem in the calipers? In thinking through what might have gone wrong, and coming to no answer, I also came up with this question – What actually makes the pistons move back into the caliper and draw the pads away from the rotor when the brake lever is released?
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Have a safe ride everyday!
Doug Utt

[Ted]

Clogged master cylinder relief hole?

Here is a good thread on MC rebuilds:
http://www.k11og.org/forum/viewtopic.php?t=6897

Note the reply about checking the relief hole.

EDIT - haha, just saw this exact same thing in this month's Owners News - the guy cleaned the relief hole with a sewing needle and compressed air.
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Ted
KOG#1

[Flying Duck]

You may have some dislodged "junk" clogging the brake lines. If that's the case then taking all of the brake lines/banjo bolts off and cleaning them thoroughly. A fair amount of work but at least you don't have to deal with ABS so shouldn't be too much work.

If the problem is in a caliper then I don't know as I've never rebuilt one.

When I got my RS, the front brake was sticky. I could resolve it temporarily by merely pushing the brake lever back out. Resolved it for good by pulling the pivot for the brake lever and cleaning/lubing it.

If you're referring the the master cylinder piston when you refer to the actuator rod then you just need to get it far enough in so that the set screw will hold it. There's nothing to measure. If you messed with the little adjusting bolt with blue on it then I suppose it's possible that if you push the piston in far enough it could stick. I've only had that issue with over-adjusting the rear master though.
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93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

[Saltcreek]

That's the best written description of a problem I've seen in almost two years here.
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Jim

1994 K1100LT Mystic Red, bfd, 37000 miles, sold
2009 Wilderness Systems Zephyr 155 ST
2002 Litespeed titanium

[Stoked Steve]

I agree with the debris in the line or possibly the delamination of the interior of the brake lines creating a "one way" valve that we've read about from others.
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Steve
Virginia Beach, VA
93 K1100RS Mystic Red SOLD
12 Suzuki DL650A VStrom

[Stoked Steve]

[tmarshall57]

I've read the original post and can confirm that exactly the same thing happened to me following a M/C rebuild. My M/C build was undertaken for exactly the same reason as the OP.

I also couldn't explain the cause. I had been meticulous in cleaning the M/C and in ensuring sufficient play was evident at the brake lever. I could only conclude that I had incorrectly adjusted the pin connected to the handlebar lever and which depresses the M/C piston. I don't think there is a published specification for this adjustment.

Luckily, althought the pads were smoking, no lasting or espensive damage was done.
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K1100RS Special Edition 1997
Arctic Silver/Black

[robleyd]

[Scott_Anderson]

[Stoked Steve]

[BobZ(IL)]

Ridetoday,

My front brake was slow to release. Several ideas were put forth here, so off I went.

!. Rebuilt master cylinder, no help.

2. Rebuilt calipers, no help.

3. Replaced, front brakes lines, alas, success.

Spent lots of money and felt the grief of rebuilding things that appeared in great condition once taken apart, but having proper front brakes is great.

Take your pads out and clean calipers. If pistons move in and out freely, I would try new brake lines first.

Of course this assumes m/c was cleaned and blown clear with compressed air.
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'93 K1100LT
'78 R100S
'05 R1200GS
BMWMOA, CRBMWOA, ABC, K11OG #997

Live well, do good work, enjoy the ride.

[tmarshall57]

[jpberens1994K1100RS]

There is an adjustment to lever free play. Right on the front of the lever isa srecw adjuster. The tool kit screw driver fits it.
I've been though both front & back MC rebuilds.
My front was all set, but in a moment of fiddlewithitfornoreson itis, I wanted it just a bit quicker equating a minimal amount of adjustment slack as a bad thing.
I did not get 5 blocks when I felt drag. Made a U turn, got another 2 blocks back. That was it. The front PR2 was howling as it tried to stop the bike. Adjusted the slack back in, all good.
We have all read about back brakes starting fires, usually due to incorrectly adjusted rear brake. Front is kinda the same way given all else is mechanically correct.
What helps me now is to think of that slack as a proper adjustment. Same as the clutch. Too tight or not enough slack = bad.
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1993 K1100RS that I'd rather be riding FAST!
2014 Moto Guzzi Norge

[Christopher P.]

I recently suffered the same problem on my K100. I chose to swap my MC for a used one, no problems since.

One of these days I'll dig into and perhaps rebuild the original, but it seemed like I was getting fluid bypass when there shouldn't have been, which was pressurizing the system but not letting anything out. Had to stop a couple times on the road, and pop open the zerks to let a little fluid out before I could continue.

Bad way to ride.
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www.tidewaterforge.com

[Saltcreek]

If you haven't yet, click on Christopher's web link. Amazing.
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Jim

1994 K1100LT Mystic Red, bfd, 37000 miles, sold
2009 Wilderness Systems Zephyr 155 ST
2002 Litespeed titanium

[Ted]

[Christopher P.]

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www.tidewaterforge.com