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1Back to top Go down   Rear master cylinder stuck  Empty Rear master cylinder stuck Wed Aug 09 2023, 12:05

Jakobm3ro

Jakobm3ro
active member
active member
Hey everyone

Have any one experienced that you rear master cylinder is stuck. I tried to open the cylinder and cleaned every part then reinstalled it, but still get stuck when I give it hard push in. 

I will like to order a new master cylinder repair kit , but I’m not sure if that will help my issue. 

Hope you guys can help a new bmw k1100 (93) owner.  cheers cheers

    

2Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Wed Aug 09 2023, 12:52

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
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
    

3Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Wed Aug 09 2023, 13:55

Jakobm3ro

Jakobm3ro
active member
active member
Hi,
Thank you for the link. I don’t believe that’s the issue. There is free play. I have detached the cylinder ann pushed it out with a compressor, and when I push it with hand power it get stuck again after a full push it to the bottom.

The cylinder inside is all cleaned and air cleaned, and looks not damaged. I’m wondering if this issue course the pump inside and need to be replaced?

    

4Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Wed Aug 09 2023, 15:28

Suzi Q

Suzi Q
Life time member
Life time member
Does it get stuck when you have it disconnected, on the bench, and with no fluid in it except a little bit for lubrication?


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

5Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Wed Aug 09 2023, 15:37

MartinW

MartinW
Life time member
Life time member
Do you have the spring in place under the piston? One of the K  Kronies had problems with his front master cylinder due to an error when assembling. The manual showed the spring in front of the piston instead of behind.
Regards Martin.


__________________________________________________
1992 K75s
    

6Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Wed Aug 09 2023, 15:40

duck

duck
Life time member
Life time member
Suzi Q wrote:Does it get stuck when you have it disconnected, on the bench, and with no fluid in it except a little bit for lubrication?

Because it should not stick when installed with a fully bled system with no air in the lines or caliper and the pedal properly adjusted.  

On the bench there's nothing giving it resistance.


__________________________________________________
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
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
    

7Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Wed Aug 09 2023, 17:01

Jakobm3ro

Jakobm3ro
active member
active member
Suzi Q wrote:Does it get stuck when you have it disconnected, on the bench, and with no fluid in it except a little bit for lubrication?
Yes it get stuck as well. 
I have an other master cylinder which is working but the thread is broken, this does not get stuck. And I can’t use the kit since it’s a 13 mm an mine is 12mm cylinder

    

8Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Thu Aug 10 2023, 01:43

Suzi Q

Suzi Q
Life time member
Life time member
Well in that case it can only be either a damaged bore or piston, or a seal swollen because of contact with an unsuitable cleaning fluid for example. 

Edit: did some of these master cylinders have a M4 cap screw in the side for some strange reason, that could jam the piston if it protruded too far into the bore - or am I thinking of something else?

Edit (again): Yes they did, I'm not dreaming! I've just checked the Madass which has an OE master cylinder. I remember an issue with the M4 cap screw in the side of the cylinder body. Have you got such a screw, and could that be the cause?


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    


10Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Thu Aug 10 2023, 07:02

Jakobm3ro

Jakobm3ro
active member
active member
duck wrote:
Suzi Q wrote:Does it get stuck when you have it disconnected, on the bench, and with no fluid in it except a little bit for lubrication?

Because it should not stick when installed with a fully bled system with no air in the lines or caliper and the pedal properly adjusted.  

On the bench there's nothing giving it resistance.
You are right, I’m trying to not push it all in while bleeding the system -but it’s difficult.. 

If I get it bleed out it will work probably. Is it sustainable to have a cylinder that may get stuck again..

    

11Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Thu Aug 10 2023, 07:34

Suzi Q

Suzi Q
Life time member
Life time member
I'm confused now. 
Duck's point is that, if the brake pedal is so badly adjusted that it does not allow the cylinder piston to fully retract when released, then the port from the reservoir may not be uncovered, which means that the system becomes starved of fluid leading to the cylinder piston not fully retracting.
But you've said that the problem is still there when the cylinder is disconnected and on the bench?


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

12Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Thu Aug 10 2023, 08:50

Laitch

Laitch
Life time member
Life time member
Jakobm3ro wrote:If I get it bleed out it will work probably. Is it sustainable to have a cylinder that may get stuck again..
Is what sustainable—your life? I would not place bets on that if your motorcycle's brakes are unreliable. Laughing

    

13Back to top Go down   Rear master cylinder stuck  Empty Re: Rear master cylinder stuck Thu Aug 10 2023, 14:19

Jakobm3ro

Jakobm3ro
active member
active member
Suzi Q wrote:I'm confused now. 
Duck's point is that, if the brake pedal is so badly adjusted that it does not allow the cylinder piston to fully retract when released, then the port from the reservoir may not be uncovered, which means that the system becomes starved of fluid leading to the cylinder piston not fully retracting.
But you've said that the problem is still there when the cylinder is disconnected and on the bench?
Correct, and now after fighting with the piston to get it out of the cylinder, it get stuck immediately when I try to push it in. I believe that’s it, I have to get a new one. It’s risky business..

    

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