More R1150RT Brake questions

Hi all,

I have a 2003 R1150RT-P that is exhibiting a brake issue. I have been searching for a few days but haven't found my exact symptoms.

The bike had stripped input shaft spines when I got it a few years ago. Over the past few months I have been fixing it up. I replaced the transmission and clutch, and finally put a battery in it.

At first the ABS light would start to flash followed by the rapidly flashing brake failure warning light. After doing some research on the forums, I noticed the brake light was on all the time. After a little bit of adjusting, the brake light behaves as expected and the lights go through self test and turn off. The ABS light goes out once the bike is moved. ...all good, I thought...

On my first test drive, I noticed there is no braking from the rear brake pedal. My symptoms are as follows.

ABS system passes self test.

Whirring sound from the servo that does not change in pitch when pressing the rear brake with the power on.

Whirring sound from the server that does change in pitch when squeezing the front brake lever.

No braking at all from the rear pedal when depressed with power on or off.

Braking at the front when using the front lever with power off.

Braking at the front and rear when fully activating the front brake lever with the power on.

ABS works fine using the front lever.

My understanding of the system leads me to believe that the front and rear wheel circuits are fine (working rear brake from front lever)

I expect the problem is with the rear control circuit.

Does that sound about right± (sorry, typing on a Japanese MacBook with no question mark key)

I don't want to just throw parts at the bike, so...

Is there any way to test the rear master cylinder±

Is there any other component likely to cause the current operating condition±

What specialty tools would I need to bleed the rear control circuit±

Are there any other tests I can perform before starting to place parts on order±

Other than that the bike is in really good shape. I little bit of surging, but I still need to adjust the valves and sync the throttle bodies.

I look forward to hearing from the experts on this forum.

Hi all,

 

I have a 2003 R1150RT-P that is exhibiting a brake issue. I have been searching for a few days but haven't found my exact symptoms.

 

The bike had stripped input shaft spines when I got it a few years ago. Over the past few months I have been fixing it up. I replaced the transmission and clutch, and finally put a battery in it.

 

At first the ABS light would start to flash followed by the rapidly flashing brake failure warning light. After doing some research on the forums, I noticed the brake light was on all the time. After a little bit of adjusting, the brake light behaves as expected and the lights go through self test and turn off. The ABS light goes out once the bike is moved. ...all good, I thought...

 

On my first test drive, I noticed there is no braking from the rear brake pedal. My symptoms are as follows.

 

ABS system passes self test.

Whirring sound from the servo that does not change in pitch when pressing the rear brake with the power on.

Whirring sound from the server that does change in pitch when squeezing the front brake lever.

No braking at all from the rear pedal when depressed with power on or off.

Braking at the front when using the front lever with power off.

Braking at the front and rear when fully activating the front brake lever with the power on.

ABS works fine using the front lever.

 

My understanding of the system leads me to believe that the front and rear wheel circuits are fine (working rear brake from front lever)

I expect the problem is with the rear control circuit.

Does that sound about right± (sorry, typing on a Japanese MacBook with no question mark key)

 

I don't want to just throw parts at the bike, so...

Is there any way to test the rear master cylinder±

Is there any other component likely to cause the current operating condition±

What specialty tools would I need to bleed the rear control circuit±

Are there any other tests I can perform before starting to place parts on order±

 

Other than that the bike is in really good shape. I little bit of surging, but I still need to adjust the valves and sync the throttle bodies.

 

I look forward to hearing from the experts on this forum.

Morning Mark

It does sound like a rear control circuit problem like lots of air in the rear control circuit or the rear master cylinder isn't building any pressure.

Did you get much fluid out of the servo bleeders for the rear control circuit when you bled that?

The rear pedal up stop needs to be set perfectly for the rear master cylinder to properly uncover the take-up port & allow new fluid in (is the rear pedal & switch reed adjusted to BMW manual specs??????)

Did you remove the little rubber bladder from the rear fluid reservoir to add fluid to the reservoir?

There was also a BMW service bulletin on your exact problem but it was for 1150RT's built during the month of April of 2004 so it shouldn't be on your bike. (it supposedly only effected 180 U.S. imported 1150RT's)

BUT!- someone could have installed an April 2004 rear master cylinder at one time in the past in the bikes life.

So inspect your master cylinder for the production date-- BMW 140434, if a 140434 cylinder then you probably have a master cylinder with incorrect internal sealing rings.

The production date code is stamped on the master cylinder's flange between the 2 mounting points.

D.R.

The depth of your knowledge on these bikes never fails to amaze me.