2005 R1200ST - no rear brake

[RANBUSH]

2005 R1200ST - the gift that keeps on giving; I went out to ride this bike recently, and the rear tire was flat. It seems that a three-year old plug from an old flat had failed. OK, understandable, no problem. I bought a new rear tire online and waited for it to arrive.

The new tire arrives, I pull the wheel and mount the new tire. Air it up, the bead sets, I'm happy.

So this week I go out to ride the bike and the rear brake lever goes all the way down to the stop, no rear brake pressure at all. Front brake works fine. I dismount as the bike is idling and I notice there are small but noticeable whisps of smoke coming from the middle of the bike on the lower left side - never a good thing on a motorcycle!

I shut off the bike and let it cool down. I notice a wet spot on the garage floor below where the header joins the muffler. I stick my finger in it and smell it, and taste it (yeah, I know, I know) and it isn't oil, it isn't water, it's brake fluid.

Yesterday I pull off the body work and there is still brake fluid in the rear brake master cylinder. I don't see any obvious leaks or wet spots in the lines, or on the garage floor.

I call my Smart Motorcycle Buddy and he suggests that maybe it is NOT brake fluid, it may be fluid leaking from the hydraulic clutch slave cylinder, which is also in the area above where the header joins the muffler.

I open the clutch master cylinder at the handlebar and there is plenty of fluid. The clutch works fine. I drain the brake fluid out of the brake master cylinder, pump the rear brake pedal a few times, and there is no obvious fluid leaking from the brake lines that I can see.

I fill up the brake master cylinder, pump the rear brake pedal a few times, and set a piece of cardboard under it overnight. No wet spot this morning. Start the bike up, and there is no more smoke, but still no rear brakes.

So (if you're still reading this lengthy plea for help), is the 19-year-old clutch slave cylinder a suspect, or are the 19-year-old brake line connections and rear master cylinder the suspect?

 

[AntonLargiader]

He says the 2005 R1200 bikes use DOT 4 in both the clutch lines and the brake lines.

What does it say on the clutch reservoir cover?

The clutch works fine....and there is no more smoke, but still no rear brakes.

So (if you're still reading this lengthy plea for help), is the 19-year-old clutch slave cylinder a suspect, or are the 19-year-old brake line connections and rear master cylinder the suspect?

How would your perfectly functioning clutch system give you no rear brakes? I'd be looking at the rear MC. But you should still be able to bleed it and get function, even if just for a while.

 

[pauls1150]

The MAX fiche shows that the brakes are DOT 4, but the clutch uses something called

​

21 52 2 455 540​

TRANSMISSION OIL HYSPIN V10​

This looks like the biodegradable "vegetable oil" ... so if you have had DOT 4 in that circuit, you likely need to completely drain it, FLUSH it, and replace a few seals...

Hopefully you don't have that stuff in your brake circuit - it cannot withstand the heat generated by braking; dunno about those seals...

 

[RANBUSH]

> This looks like the biodegradable "vegetable oil" ...

Yes thanks for the thought, the fluid in the clutch reservoir has a bluish tint to it. The fluid in the brake reservoir is yellow.

I will try bleeding the brake MC and see if that does anything. Thanks for the suggestion, Anton.

 

[drneo66]

Hyspin is blue mineral oil. You can buy it from BMW for $$$ or head to your local mountain bike shop and spend way less on Magura Royal Blood

https://www.nippynormans.com/r-nine-t-family/hyspin-v-10-clutch-fluid-250ml

https://www.beemerboneyard.com/magminoil.html

 

[69ZEFF65]

ABS Whizzy (servo) ? ABS non servo? No ABS? If its the Whizzy ABS there is a particular way to bleed the brakes and you don't do it tthat way you will run into problems like no brakes.

 

[AntonLargiader]

Thanks Zeff, I overlooked that the 2005 would have iABS.

@RANBUSH, provided you have ABS, it's a bit more complicated and you should look at some videos on bleeding those brakes. The visible MC and reservoir are part of the control circuit which basically operates the ABS unit, which in turn has a different hydraulic circuit that operates the caliper. If you add fluid at the reservoir and pull it out of the caliper thinking it's the same circuit, you'll just empty the wheel circuit like they did in Long Way Round.

If you don't have ABS, and I think there were some of those sold here, then this doesn't apply.

EDIT: the fluid in the pic is leaking where it would if the ABS unit reservoir overflowed, which isn't unusual when the caliper pistons are pushed back all the way. By itself that isn't a problem, but you don't have rear brakes so you'll want to see if that is coming from one of the hoses. You'll need to bleed the system to assess that.

 

[lee]

If it's servo brakes it's easy to miss seeing the rear reservoir has two chambers.

 

[AntonLargiader]

I think the K41 (K1200) was the only time that split reservoir was used. On the boxers the ABS unit was always mounted upright, and the control reservoirs look just like non-ABS.

 

[lee]

I think the K41 (K1200) was the only time that split reservoir was used. On the boxers the ABS unit was always mounted upright, and the control reservoirs look just like non-ABS.

Thanks for the correction so the OP does not get confused.

 

[RANBUSH]

... provided you have ABS, it's a bit more complicated and you should look at some videos on bleeding those brakes.

Thanks, Anton, I appreciate your follow up. You too, Zeff and Lee. I will study up and report back.

 

[RANBUSH]

Thanks again to all that have offered help.

This week I pulled the fuel tank and got a good look at the ABS unit (I failed to mention in my original post that this 2005 ST bike has the "whizzy" brakes, servo-assist, noisy iABS). So I looked at my Jim Von Baden DVD and tried to bleed the rear brakes. No joy.

I also want to remind everyone that a month ago I _did_ have rear brakes when I mounted a new rear tire.

I found that there is a connector on the ABS unit that is blowing air (soapy water) when I pump the rear brake pedal. It is in a really tight area, and hard to get at. But I can push and pull on the hard line that goes into the connector, not a good sign. Pushing down on the hard line reduces the soapy water bubbles.

Does anyone know what type this connector is, is it supposed to be threaded in, and how do I get in there to pull off the cap to see if it has un-threaded itself?

TIA.

 

[kinterridge]

I'm pretty sure it's a cover cap with a circlip of some sort under it with an "o" ring. The "o" ring maybe has failed. "o" ring needs to be able to handle your type of fluid. Hope this helps.

 

[bewareboy]

My recollection is that the tube is held into the unit with a clip. Pull up the soft black cap and you should see the clips. Pull the clip out and the tube should be removable. If there is no clip, that would be a problem. Check the other 3 tubes while your at it. Max BMW part fiche shows an OK illustration.

 

[RANBUSH]

Thanks guys, I'll check your ideas out this weekend and report back. It's one of those motorcycle problems where "it worked last ride/week/month, and now it doesn't work".

Should be a simple explanation.

 

[RANBUSH]

Thanks to those that suggested "circlip". I got in there today and that's what it was, the circlip on the hardline to the rear brake port on the ABS controller had somehow popped off. I have rear brakes again now.

I bet this will also solve the mystery of fluid dripping onto the muffler, but I'll have to put the fuel tank and the bodywork back on to find out.

Thanks again to all those that offered suggestions.

 

[RANBUSH]

> I'll have to put the fuel tank and the bodywork back on to find out.

Got the fuel tank and the bodywork back on today, started it up, and as hoped, no more fluid dripping, rear brake works fine. Test ride tomorrow to make sure.

Thanks again to all that replied.

 

[RANBUSH]

So, on the test ride the brake warning lights won't go out after activating both front and rear brakes. Back into the shop and plug in the GS-911. Error code is "low brake fluid" but the diagnostic readout shows that the GS-911 thinks the _front_ brake is activated when I press on the _rear_ brake lever, and vice versa.

I call the GS-911 support guy at Beemershop, and he says that my symptoms indicate the ABS Pump may be failing.

I've seen one youtube video / heard of removing the ABS Pump and just riding with mechanical brakes, with no ABS assist. Any input from the Smart Guys here?

TIA.

 

[AntonLargiader]

First things first: is the fluid level low in either of the wheel circuit reservoirs? These are the ones in the ABS unit.

 

[RANBUSH]

First things first: is the fluid level low in either of the wheel circuit reservoirs? These are the ones in the ABS unit.

Yes Anton, I'm getting a "low brake fluid" fault code in the GS-911 report.