K11 Owners Group

storch · Posted: Wed Apr 06, 2011 3:12 pm Post subject: front master cylinder leak

Bleeding brakes on my K1100 LT 1997 I have fluid leaking from front master cylinder.Took it apart,inside is very clean.How is the piston retainig screw(Allen head,about 4 mm)) sealed?could that be the source of leak?
Gary

Flying Duck · Posted: Wed Apr 06, 2011 3:55 pm Post subject:

Did you push the pads apart to take the calipers off and check the pads? If you did then that can push fluid past the master cylinder seals. In the future attach a hose to the bleed valve on the left caliper and open it while you're taking right caliper off and vice versa for the other side. That keeps pressure from being pushed back up to the master cylinder when the pads get pushed apart. This is also a good technique to use when you have to push the pistons in to install new brake pads.

The set screw has a 3mm Allen head.
_________________
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

Al. · Posted: Thu Apr 07, 2011 4:41 pm Post subject:

this happened me - the front seal was worn (next to lever)
On close examination I could see tiny score marks on seal.

Number 6 · Posted: Sat Apr 09, 2011 3:02 am Post subject:

I'd advise replacing it with the anodized master cylinder that was introduced on the R1100, that's the same one with a surface treatment that makes it more durable.

Edited for a more precise information: check that the master cylinder part# is 32722352190, otherwise you might get the old non-anodized master cylinder from an early R1100
_________________
I am not a number, I am a free man.

94 K1100LT

Flying Duck · Posted: Sat Apr 09, 2011 7:42 am Post subject:

Number 6 · Posted: Sat Apr 09, 2011 10:26 am Post subject:

Flying Duck · Posted: Sat Apr 09, 2011 11:26 am Post subject:

I checked and the part was not superceded until May 14, 1999 (I have the OEM parts catalog) so ALL K1100s came with the earlier one as did all R1100s built up to that date so just getting one from an R1100 doesn't work unless you make sure the R1100(or R850) is model year 2000 or later.

And I'm still curious as to exactly how they improved it, if you know.
_________________
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

Number 6 · Posted: Sat Apr 09, 2011 1:08 pm Post subject:

I don't know exactly, some hardening deposit I guess, like nikasil on cylinders. I had the information from a mechanic, from his experience, those mc are much more durable.
_________________
I am not a number, I am a free man.

94 K1100LT

Flying Duck · Posted: Sat Apr 09, 2011 2:11 pm Post subject:

Manufacturers do not change the design/manufacture of parts without changing the part number. It's called supercession. This is especially true on items like brake components which are a critical safety item and as such may be subject to a recall. The BMW OEM parts catalog I have shows the part changed in May of 1999. I find that to be a much more reliable source than second hand heresay from a mechanic.

In this case, the mechanic was only half right as R1100s, R850s built prior to the May 1999 supercession would have the same master cylinder as K1100s.

I see all sorts of bullshit rumors about K parts on the Internet which I know for a fact not to be true. Therefore, I only believe that which can be documented.
_________________
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

Number 6 · Posted: Sat Apr 09, 2011 2:41 pm Post subject:

Well, you can dismantle the mc and check for yourself, this is a reliable information.
_________________
I am not a number, I am a free man.

94 K1100LT

Bob T · Posted: Sun Apr 10, 2011 3:28 pm Post subject:

Didn't I read some posting about MC leaking that quits after a while?
I believe it had to do with working on the system, forcing fluid back out of the MC, but eventually it quits coming out?

I'd like to know, because now have this situation and I'd rather not rebuild/replace if it is not necessary...
_________________
Bob T.
'96 K1100RS
'95 K1100RS - Totaled
'01 Triumph TT600
'83 Suzuki GS1100E

Number 6 · Posted: Sun Apr 10, 2011 3:46 pm Post subject:

Honestly, I wouldn't count on it.
_________________
I am not a number, I am a free man.

94 K1100LT

Flying Duck · Posted: Sun Apr 10, 2011 4:08 pm Post subject:

Flying Duck · Posted: Mon Apr 11, 2011 2:55 am Post subject:

Number 6 · Posted: Mon Apr 11, 2011 3:01 am Post subject:

Well, this is a forum, if you don't find my advice valuable it's up to you, but you are not alone here and other people may benefit for that information.
_________________
I am not a number, I am a free man.

94 K1100LT

Flying Duck · Posted: Mon Apr 11, 2011 3:11 am Post subject:

Number 6 · Posted: Mon Apr 11, 2011 3:27 am Post subject:

Check here: http://www.realoem.com/bmw/showparts.do?model=0526&mospid=51710&btnr=32_0784&hg=32&fg=72&hl=24&lang=enUS it says "Cylinder with piston, anodized" and I believe the previous ones were not anodized.
Now once again, I give an advice, I am not going to spend hours proving my point is right, if you don't believe me, too bad for you, period.
_________________
I am not a number, I am a free man.

94 K1100LT

Flying Duck · Posted: Mon Apr 11, 2011 3:30 am Post subject:

I'd really like you to explain how BMW was producing two different master cylinders under the exact same part number at the same time and only putting the shitty ones on K1100s. This should be good. Laughing

_________________
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

Number 6 · Posted: Mon Apr 11, 2011 3:36 am Post subject:

Why do you say "same part number"???
_________________
I am not a number, I am a free man.

94 K1100LT

Flying Duck · Posted: Mon Apr 11, 2011 3:44 am Post subject: