BMW K bikes (Bricks)

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JDiggamus

JDiggamus
active member
active member
Hi Again,  My front brake master cylinder is leaking.  It leaks right where the lever and cylinder meet,  I took the lever off and there was a lot of fluid in there.  Any suggestions on how to fix it and where to get parts?  I'm in the US.  

Thanks!


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--------------------------------------------
1984 BMW K100RS
Los Angeles, CA
last 7 of VIN# 0019268
;BMW;
    

duck

duck
Life time member
Life time member


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

MarcS

MarcS
Silver member
Silver member
I pulled mine apart and gave it a light rub/hone with some fine emery paper. Rub it around inside dont rub backwards and forwards, if that makes sense. This worked for me for a while but leaked again after a couple of months. I got the parts from the UK. I cant remember the supplier but I am sure that someone here will know them.


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K100rt ex plod bike 5/1990.



I have no problem with authority. Just some of the morons that are paid to enforce it.
    

td5

td5
Gold member
Gold member
HI,
I had to replace mine so Motobins or motor works in the UK are your best bet for a new unit.
Cheers
Mike


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Front brake master cylinder leaking break (brake) fluid K_engi10
1988 / K100RS
2013 / R1200GS
2015 / K1300R
    

5Back to top Go down   Front brake master cylinder leaking break (brake) fluid Empty Thanks, but encountered another problem on Fri Apr 12, 2019 2:42 am

JDiggamus

JDiggamus
active member
active member
Ok, so I decided to take all of your advice (thank you)  but i didn't allow enough time for the job so i was in the process of taking off the right handle unit and removed the 2 Allen screws and to the brake handle off as well as the bolt underneath that attaches to the actual brake line (i think) I also disconnected the cable that connects to the brake handle (not the throttle cable) .  Well, I couldn't get the unit that houses the reservoir off and I decided that I bit off more than I could chew and that I would come back to it when I had more time, I had to leave for a meeting and my bike was my only form of transport.  So I put everything back the way it was but when I tested the front brake there was zero resistance, I could squeeze the handle in all the way without any tension.  It did still engage the front brake though and the brake were working but it felt completely different.

Any ideas as to what I did wrong and how to fix it?

Thanks again, everyone.  Complete noob here and I'm learning as I go and getting my hands dirty.


__________________________________________________
--------------------------------------------
1984 BMW K100RS
Los Angeles, CA
last 7 of VIN# 0019268
;BMW;
    

chris846

chris846
Life time member
Life time member
You say the brake is still working, don't know if that's exactly what you meant, but IT ISN'T. Don't try and ride it. It's one thing for a brake to lock a wheel in the workshop, but on the road it'll be like you have no brake at all. 

Have a look at some exploded diagrams and see if you can figure out how it all comes apart. It's straighforward and all of us had to learn. The problem you've got doesn't seem out of the ordinary, maybe a sticky piston or leaky seal or both. Duck has already posted the absolute best starting advice - strip and clean it.

But, unless you are a good learner in these things, and with it being your front brake too, do you know anybody who can look over your shoulder with this one?


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The Longest Lunch
    

charlie99

charlie99
VIP
VIP
probably has air bubbles in the fluid  pressure line now ...which compress giving a really weird feel to the action

a possible solution is to undo the cap on the fluid reservoir ...and park the bike on the sidestand   over night ....this may let the bubbles return to the reservoir

another solve could be to do as above and in addition ...hold the brake lever back to the bars with a rope ...tie wire or something  so that the piston is pushed in as far as it can go into the cylinder ...again were hoping that the air bubbles return to the reservoir ....

in reality the front brake system should be bleed through to the callipers before attempting this ...to be sure ..


just a heads up ..that may  help

good luck


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OFront brake master cylinder leaking break (brake) fluid Au-log10

"redframe" rs "bitsa"  with many contributions from the k100 community ,,with many thanks
    

8Back to top Go down   Front brake master cylinder leaking break (brake) fluid Empty Front Brake on Fri Apr 12, 2019 6:19 am

redrockmania

redrockmania
Silver member
Silver member
Charlie's post is an excellent comprehensive summary about brake  bleeding (problems). and what to do. If you are going nuts trying to get rid of air in the system, often leaving it overnight will see the trapped air bubbles released. Two other things worth mentioning. There are brake bleed nipples called "SpeedBleeders" as a quality after market substitute that are a big help if you are bleeding brakes without an assistant. There is another brand (I think German) of similar design to SpeedBleeders that has a good reputation BUT the best device I ever purchased for hydraulic fluid bleeding is a Mityvac. With a Mityvac you can bleed hydraulic lines easily as a 1 person operation and the trapped air is quickly removed. Mityvac's are easy to find on eBay and they are well made  - should last you a lifetime. You also are much less likely to spill hydraulic fluid during the bleed process. Hope this helps.

    

duck

duck
Life time member
Life time member
Speed bleeders are great for cars but you really don't need them on a motorcycle.  Unless you only have one arm you can easily operate both the brake lever with one hand and a wrench on a normal bleeder with the other.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
@chris846 wrote:You say the brake is still working, don't know if that's exactly what you meant, but IT ISN'T. Don't try and ride it. It's one thing for a brake to lock a wheel in the workshop, but on the road it'll be like you have no brake at all. 

Have a look at some exploded diagrams and see if you can figure out how it all comes apart. It's straighforward and all of us had to learn. The problem you've got doesn't seem out of the ordinary, maybe a sticky piston or leaky seal or both. Duck has already posted the absolute best starting advice - strip and clean it.

But, unless you are a good learner in these things, and with it being your front brake too, do you know anybody who can look over your shoulder with this one?
Excellent advice.

All I use for bleeding is an 11mm/7/16" box end wrench, 3 feet of 1/4" clear vinyl tubing, and a gallon jug half full of water.  Stick the end of the tubing into the handle of the jug so it can't come out.  The water dilutes the brake fluid so it can't hurt anything if you spill it, and also keeps the jug from tipping over.


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Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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