K11 Owners Group

malcolmt · Last edited by malcolmt on Wed Feb 03, 2010 1:55 pm; edited 1 time in total

I’ve just replaced the rear brake master cylinder on my 92’ K1100RS.
I cant seem to get it bled dispute being able to pump plenty of fluid through the system.
My first step was to bleed to the nipple on the servo. I push the peddle down and crack open the nipple, then I repeated at the calliper. When I push the brake peddle it feels as if the fluid is leaking as it goes to the stop. There are no leaks, can it be the servo or are there special tricks to do the job.

Thanks
Malcolm
Joburg
South Africa
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A Bike on the road is worth two
in the shed
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Stoked Steve · Posted: Tue Feb 02, 2010 3:33 pm Post subject:

It does take a long time to bleed all the air out, especially after something as major as replacing the M/C. Are you still getting air bubbles? When I did mine last year I thought I'd never get all the bubbles out, but eventually did.

Just keep going until there are no more bubbles at both the ABS pump and the caliper, keep going back and forth until the fluid is bubble free.

I don't think there is any special trick.
_________________
Steve
Virginia Beach, VA
93 K1100RS Mystic Red SOLD
12 Suzuki DL650A VStrom

BMGraeme · Posted: Tue Feb 02, 2010 4:35 pm Post subject:

The problem is priming the MC - try squeezing the feedpipe to the reservoir. If you notice bubbles keep doing this. If that fails you could try filling the MC with fluid before connecting up the system to help prime it but be very careful with the fluid as it strips paint very easily. Thats what eventually worked for me.
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1980 CB900FA
1994 K1100RS
2008 R1200GSA

malcolmt · Posted: Wed Feb 03, 2010 2:20 am Post subject:

Is there a chance a faulty servo can cause the problem ??

The initial problem was the back brake stopped working, I could push the peddle down to the stop and still rotate the wheel. A little fluid was weeping out of the master cyl so i decided to replace the complete unit.

The new cylinder is behaving the same, so either i've not fully bled it ( there are no signs of air in the fluid) or there's another problem..and the only other problem i can think of is the servo.

I'll have another shot at bleading it, it that dosent work then I'll connect the master cylinder directly to the caliper for a test. That will eliminate the servo. If it is the servo then maybe its time to scrap the ABS.

Malcolm(t)
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A Bike on the road is worth two
in the shed
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malcolmt · Posted: Wed Feb 03, 2010 1:53 pm Post subject:

Hi All,

This evening I connected the master cylinder directly to the caliper.... Shocked

The brake bled easily and the brake pedal is now solid, so the problem seems to be the servo leaking.
Is there anything which can be done to resurrect a servo, there is a large nut at the top, can this be removed. If so what’s inside ??

Can anyone explain where the fluid goes as the servo drops the pressure on the caliper, I’m wondering if there is a cavity which needs to be filled and maybe there is a problem with the method I’m using to bleed the system.

Malcolm(t)
Joburg
Souf Efrica
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A Bike on the road is worth two
in the shed
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Mystic Red · Posted: Wed Feb 03, 2010 7:15 pm Post subject:

I'll bet you just have air in there. A power bleeder can help. Don't take it apart! Smile

_________________
Scott Hespelt, '94 K11LT
K11 OG #466

heatmizr · Joined: 25 Jan 2010 Posts: 16 Location: Charlotte NC

I think you're right about the servo having some reservior that the fluid can go into when operating. I was just thinking about this today.
I think your system may be ok but bleeding it correctly might be the problem.
Try a suction bleeder at the servo maybe?

I'm watching your posts with interest as I will be re-building a rear brake master cylinder on a 1996 k1100rs soon.
- Todd
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Todd Glasier in Charlotte, NC
1996 k1100rs (on loan)
2002 RC1
2000 VFR

malcolmt · Posted: Wed Feb 10, 2010 2:15 pm Post subject:

Hi all,

Here is what I’ve done to the rear brake.
I’ve fitted a 2.5cm longer brake pipe from the master cylinder to the caliper. The extra length gives me a nice vertical loop too allow for swingarm movement.
The modulator ports are plugged.

The brake bled easily and works well, the ABS light still goes out when ridden a couple of meters.
I expect the ABS is still functional on the front wheel.

Malcolm(t)
_________________
******************************
A Bike on the road is worth two
in the shed
******************************