BMW K bikes (Bricks)

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1Back to top Go down   Rear Brake Problems Empty Rear Brake Problems on Mon Aug 04, 2014 6:25 am

Grizzly

Grizzly
Silver member
Silver member
forgive me if I am asking questions that have already been extensively covered in other topics but I have not been able to find anyone having the same problems as I have yet. My problem is this;

The rear brake pedal moves only a little but is really solid once it gets to its final position. With the bike on the centre stand you can very easily still turn the rear wheel and there is plenty of fluid in the reservoir.

I have only had the bike for a couple of weeks and have not actually had much of a look at this problem yet but will hopefully be doing so today. My plans are as follows - I have already opened the bleed nipple to see if there is any fluid coming out or even a change to the firm feel of the pedal and nothing. I am therefore toying with the idea of removing the hose from the calliper to see if any fluid is making it that far and then, if it isn't, taking it off from the master cylinder itself. While I cannot actually get any fluid through it seems pointless trying to refresh the fluid as it will not get all the old stuff out.

Any ideas or suggestions would be great.


__________________________________________________
Motorbike - Silver 1986 BMW K100 0008599 - 'Kylie' - written off

New Motorbike - 1998 Honda ST1100 Pan European ex-police and still without a name yet!
    

2Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 6:50 am

Holister

Holister
Life time member
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If there is nothing coming out of your caliper/slave bleed nipple then it has to be your master cylinder and it sounds like its seized.
It shouldn't be rock hard but firm and a tiny, tiny bit squishy.
I'd be puting a new kit in both master and slave.
Cheers


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Rear Brake Problems Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

3Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 7:26 am

Inge K.

Inge K.
VIP
VIP
+1........a easier solution would be to buy a new master, but Rear Brake Problems Daler10 

Often when the piston is seized solid, the bore is corroded beyond repair.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

4Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 8:23 am

92KK 84WW Olaf

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Captain Holister wrote:If there is nothing coming out of your caliper/slave bleed nipple then it has to be your master cylinder and it sounds like its seized.
It shouldn't be rock hard but firm and a tiny, tiny bit squishy.
I'd be puting a new kit in both master and slave.
Cheers

This it the most likely. Since you will no doubt be doing a complete brake fluid change I would also open up the bleed nipple in the rear caliper just in case there is a problem there. If this bleeds fluid then a seized up caliper. But my money too is on the rear master cylinder and a new kit. I had the same thing and its a false economy only replacing part of if it has been seized for a while.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles.
    

5Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 8:27 am

duck

duck
Life time member
Life time member
If you over-adjust/tighten the rear brake then hard application of it will cause the piston to freeze on the set screw.


__________________________________________________
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
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

6Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 8:28 am

Grizzly

Grizzly
Silver member
Silver member
I have already tried with the bleed nipple open and there was no difference (as I said in the original post) and am suspecting that the master is seized. Can't afford to buy a new one but have tracked down a repair kit already. Not ordered it though until I have chance to take it apart and see if it can actually be done or if it needs replacing.

 Crying or Very sad


__________________________________________________
Motorbike - Silver 1986 BMW K100 0008599 - 'Kylie' - written off

New Motorbike - 1998 Honda ST1100 Pan European ex-police and still without a name yet!
    

7Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 8:31 am

Grizzly

Grizzly
Silver member
Silver member
@duck wrote:If you over-adjust/tighten the rear brake then hard application of it will cause the piston to freeze on the set screw.

Suspecting this is not the case as there is a gap between the adjuster and the pushrod when the pedal is fully up. Stupid question though, is there actually meant to be a gap there when the pedal is up?


__________________________________________________
Motorbike - Silver 1986 BMW K100 0008599 - 'Kylie' - written off

New Motorbike - 1998 Honda ST1100 Pan European ex-police and still without a name yet!
    

8Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 9:12 am

Inge K.

Inge K.
VIP
VIP
@Grizzly wrote: is there actually meant to be a gap there when the pedal is up?

Yes, a small opening......so you can be shure that the piston returns fully.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

9Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Mon Aug 04, 2014 9:33 am

RicK G

RicK G
admin
admin
I set my pedal so that there is about 2mm of free travel.
How far does the pedal go down before it comes to a stop, They don't have much more than 30mm travel at the best of times.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

10Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Wed Aug 06, 2014 4:13 am

Grizzly

Grizzly
Silver member
Silver member
Well yesterday, after all the running around I had to do, I separated the union from the calliper and pressed the pedal - nothing! I then worked further along the line towards the master cylinder and took the flexi-hose off and again pressed the pedal - nothing!

 Crying or Very sad 

I then fully removed the rear master cylinder from the bike and took a look at it. Well firstly the rubber around the pushrod has split and it looks like this has allowed water/dirt to get in and seize it. But there is also slight damage to the pushrod tube itself where it looks like someone in the past has been messing around with it after probably having similar issues so I have come to the conclusion that I will need to be sourcing a replacement master cylinder.

 Sad 

The question I now have though is this. Has anyone fitted a master cylinder from a different motorbike to theirs and had it working? I am sure I can more easily (and cheaply) find a good rear master cylinder and then fabricate a bracket to fit it to the bike and make it work. After all, I rebuilt a 1969 One-Ton Land Rover replica once in my garden so making a small adapter bracket should be a doddle!

Your thoughts.


__________________________________________________
Motorbike - Silver 1986 BMW K100 0008599 - 'Kylie' - written off

New Motorbike - 1998 Honda ST1100 Pan European ex-police and still without a name yet!
    

11Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Wed Aug 06, 2014 5:56 am

Holister

Holister
Life time member
Life time member
If its not refurbishable, there's gotta be a second hand one around that would be a better option.
There are a few for a K1200 and R series for sale on ebay UK. They look like they might be similar. Someone here would be able to advise.
http://www.ebay.co.uk/sch/i.html?_odkw=&_osacat=177921&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xbmw+k100&_nkw=bmw+k100&_sacat=177921&_from=R40

There's one for a K100 for sale in the US but freight might be a little pricey.
http://www.ebay.com/itm/1989-BMW-K100-RS-rear-master-cylinder-/171340024269?pt=Motorcycles_Parts_Accessories&hash=item27e4a949cd&vxp=mtr

Also you could have a look thru the Buy & Sell forum


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Rear Brake Problems Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

12Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Wed Aug 06, 2014 6:33 am

92KK 84WW Olaf

avatar
Life time member
Life time member
Used - Brake master cylinder rear 13mm up to 10/88 | BRK54351
Fits K75S, K100
Rear Brake Problems T
Rear Brake Problems Magnify_large  Larger Image
Magura master cylinder. The size is indicated on the body.
See [url=http://www.motorworks.co.uk/vlive/Shop/Parts.php?T=6&Q= BRA54351] BRA54351 [/url] for new option
£60.00 No VAT payable

Rear Brake Problems T
Stock of this item varies daily. Please call to check availability and condition

This one is in Motorworks. You might need to check how much comes with it, as in does it include the piston and seals or does it need the rebuild kit as well. I just did my front brake and only needed a rebuild kit which I got from local BMW outlet.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles.
    

13Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Wed Aug 06, 2014 7:02 am

RicK G

RicK G
admin
admin


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

14Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Tue Aug 26, 2014 3:29 am

Grizzly

Grizzly
Silver member
Silver member
Just a quick update on this for people. I ended up buying and fitting an after-market brake master cylinder and when I took the bike for MoT it passed with no advisories. The rear brake works a treat and the tester said he was very impressed with how effective it was and such a neat job of the fabrication.

The master cylinder bolts in place by sandwiching an adaptor plate I made in place with the front one of the two bolts now being situated where the rear bolt would normally go. I made an adaptor which screws into the brake pedal so that the shaft from the new master cylinder pivots and the bore and stroke of the new item are the same as the original BMW part so braking force should remain the same. I have only had chance to try it a little as later on today I am off to take my module two of my bike test and will hopefully be passing and then getting the insurance sorted this afternoon. Following that, I will be going out for my first (legal) ride of my new bike.

Incidentally, I also ended up fitting a braided brake hose and using a couple of adapter unions and making a new brake pipe for the connection to the calliper itself.

Cool


__________________________________________________
Motorbike - Silver 1986 BMW K100 0008599 - 'Kylie' - written off

New Motorbike - 1998 Honda ST1100 Pan European ex-police and still without a name yet!
    

15Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Fri Sep 26, 2014 10:36 pm

robmack

robmack
Life time member
Life time member
Kaptain Holister wrote:If its not refurbishable, there's gotta be a second hand one around that would be a better option.
There are a few for a K1200 and R series for sale on ebay UK. They look like they might be similar. Someone here would be able to advise.
I have the same question about the K1200 rear MC but I see there were no answers. So, can the K1200 rear MC replace a leaking K75 rear MC (in a non-ABS rear brake setup) ?


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

16Back to top Go down   Rear Brake Problems Empty Re: Rear Brake Problems on Fri Sep 26, 2014 11:02 pm

RicK G

RicK G
admin
admin
Here is a guy who re-sleeves them in your area http://www.johnstuartpowerbrake.com/Master-Cylinders-Wheel-Cylinders.page
I have had about 5 M/C done over the years and all have been good and a stainless sleeve will outlast the bike.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

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