2003 K1200RS brake system question

[k547]

2003 K1200RS

I looked in both the factory manual and the Clymer and did not find any useful guidance regarding this but in my current mood I wouldn't be surprised If I missed something!!

Bike and brake system were functioning 100% normal, no issues.

I replaced the front and rear shocks and replaced the fork seals and dust covers and did not do anything to the brake system EXCEPT:

When I removed the front calipers I was able to raise the front end quite high and with a combination of wiggling the calipers around and dropping the front wheel almost straight down the calipers both came off without disturbing the position of the pads/pistons. No brake lines or reservoirs were touched/disturbed in any way. The calipers were then properly suspended, not hanging by the brake lines.
While the calipers were off the front and rear brake lever/pedal were never touched. The key was never in the bike. The brake system was never energized.

To re-install the front calipers I put a nylon/polymer tire iron between the pads of first the left caliper and then the right caliper and pushed them apart further to gain clearance to fit the calipers over the front brake rotors with the wheel in place. After the front calipers were re-installed I squeezed the front brake handlebar lever (with NO power on) to move the fluid back into the calipers and push the front brake pads/pistons back into position.

Apparently that was a big mistake.

The lever went to the grip 3 times with no change in feel and I stopped. A couple ounces of brake fluid appeared on the garage floor coming from somewhere ahead of the rear tire and behind the exhaust collector. On my back on the floor with a flashlight I could not determine where it came from. I put the key in and energized the bike without attempting to start it. It was in the flashing light "Brake Failure" mode with no servo whir. I did not touch the brake lever. I turned the key off and left it.
So that's where I'm at now.

 

[52184]

When you pushed the caliper pistons back it forced fluid into the front brake reservoir, which is one half of the dual reservoir on the RH side of the bike above the rear brake master cylinder. Easier to see once you remove the rear RH body panel.

That reservoir has two sections, one for front brake and one for rear. They are vented to atmosphere via a rubber tube running from the reservoir cap up and to the rear, then curved downward. They discharge at a point near the rear wheel but usually do so without depositing fluid on any body or frame parts.

So, you need to remove bodywork and top up the reservoir, and it’s is difficult to see the inside reservoir level. That’s part of a complete system bleed/refill, which you are probably going to need also at this time. The procedure is documented on the web and in the factory service manual, tho the web version is much easier to follow.

http://users.rcn.com/dehager/service/service_abs3.pdf

https://www.k-bikes.com/attachments/drain-fluids-k1200rs-pdf.13666/

https://www.youtube.com/watch?v=TpI05pWUp-Y

Also—if it hasn’t been done yet that vintage bike is overdue to have all the rubber brake lines replaced with braided stainless lines, like Spiegler. OEMs degrade and start sloughing black particles that raise cain with the ABS system.

Best,
DeVern

 

[k547]

hello DeVern,

Thanks for responding.

My bike has all braided stainless lines, fresh fluid, recent flush, etc, etc. Everything in brake system in good working order and maintained per a 20 year old bike.
Sounds like I pushed fluid out of the overflow tube of front brake portion of the rear mounted reservoir.

The rear body work is still off from the rear shock replacement. I need to find that reservoir overflow tube end in daylight.

I'm used to pushing pads/fluid around in other brands of motorcycles butt the brake system on this bike is distinctly different from other motorcycles.

Not understanding why I would need complete system bleed/refill after losing 1-2 fluid ounces thru an overflow tube...?

 

[52184]

Well, it’s possible that the level in the reservoir never dropped low enough to allow air into the system, but if it were my bike I’d top off the reservoir at the rear and check the fluid level on the control side of the circuit, up at the handlebar. Then attach the funnel and re-bleed the front brakes using the ABS pump to properly push fluid through the lines and purge air. The blinky lights you are currently getting are A) normal at first startup and disappear once the bike moves and brakes are applied, and B) often caused by the system seeing low fluid level in the front brake side of the rear reservoir.

And yes, you probably won’t need to bleed the control side of the system if that’s been done recently. On my ‘04GT with sidecar I got in the habit of running through the entire bleed process any time I had to devote attention to the brakes, just to reset the brake bleeding calendar. These bikes have awesome brakes but they do like their attention…

Best,
DeVern

 

[k547]

Well, let me put my question like this, if anyone can offer a procedure I'd appreciate it:

Starting point: Brake system fully 100% functional, clean fresh brake fluid in system, all brake pads recent, not worn down, all brake fluid reservoirs at Full markings. Both front brake calipers were removed from their fork leg mounts and then re-mounted to facilitate front shock/fork maintenance. No brake lines were opened, the brake system was not opened or disturbed in any way during front shock/fork work.

I have moved brake fluid from the front calipers back up into system by pushing the pads apart to gain clearance when I reinstalled the calipers.

Now, with the calipers in place, how do I go about pushing that fluid back into the front calipers?

Squeezing the front brake lever (as I do on my other 2 makes of motorcycles) only resulted in loss of fluid from reservoir located right/rear of bike.

I have not introduced air into the system since the handlebar and rear frame mounted reservoirs which were previously at the Full markings are now both overly full.

How do you get this fluid back into the front calipers?

 

[52184]

hello DeVern,

I'm used to pushing pads/fluid around in other brands of motorcycles butt the brake system on this bike is distinctly different from other motorcycles.

The brake system on your bike has two distinct systems—a control circuit, whose reservoir for the front brakes is at the handlebar, and a wheel circuit, whose reservoir is the inside half of the unit at right rear of the motorcycle. The two systems are bled independently and require specific procedures and sequence.

Well, let me put my question like this, if anyone can offer a procedure I'd appreciate it:

Starting point: Brake system fully 100% functional, clean fresh brake fluid in system, all brake pads recent, not worn down, all brake fluid reservoirs at Full markings. Both front brake calipers were removed from their fork leg mounts and then re-mounted to facilitate front shock/fork maintenance. No brake lines were opened, the brake system was not opened or disturbed in any way during front shock/fork work.

I have moved brake fluid from the front calipers back up into system by pushing the pads apart to gain clearance when I reinstalled the calipers.

Now, with the calipers in place, how do I go about pushing that fluid back into the front calipers?

The only correct way to move fluid from the wheel circuit reservoirs out to/through the calipers is via the ABS boost pump, as outlined in the aforementioned PDFs and video. That’s generally done using the special BMW funnel, or the BeemerBoneyard funnel, or a homemade version thereof, to assure that the reservoir stays full during the process and no air is drawn into the system.

Squeezing the front brake lever (as I do on my other 2 makes of motorcycles) only resulted in loss of fluid from reservoir located right/rear of bike.

It’s more likely the fluid loss actually occurred when the calipers were pushed back and fluid returned to the reservoir…

I have not introduced air into the system since the handlebar and rear frame mounted reservoirs which were previously at the Full markings are now both overly full.

That’s unsure at this point, if the bike has been turned on after the fluid loss occurred. The ABS pump initializes when the bike is turned on and any application of the front brake lever activated the pump, drawing fluid (or air, if the reservoir was low due to the fluid loss) from the reservoir to apply pressure to the caliper pistons.

How do you get this fluid back into the front calipers?

See above RE the funnel and documented procedure for flushing/bleeding the wheel circuits. Or, you could gamble and simply turn on the bike and gently activate the brake lever which will in turn activate the boost pump and very quickly move fluid to the caliper and push the pistons out. BUT…if the reservoir runs low you’ll draw air and still need the funnel and procedure to get the air out.

Good luck,
DeVern

 

[k547]

Thanks again,
It sounds like I will need to get the ABS pump on which up to now I have not done.
Out of curiosity I took a graduated beaker and an open can of brake fluid and recreated the spill (the mark is clearly visible on cement garage floor) and I only pumped out at the most 1/4 of a fluid oz, far less than my initial inaccurate statement of "a couple of ounces".


Just for clarification in case anyone else is trying to follow or diagnose this:

"It’s more likely the fluid loss actually occurred when the calipers were pushed back and fluid returned to the reservoir…"

No, it did not come out when the pads were pushed back. The floor was clean and dry after re-installing the front calipers and was still clean and dry about 30 minutes later when I was sitting cross legged on the floor mid point right side of the bike and reached up and squeezed the front brake lever 3 times. I looked back and actually witnessed the brake fluid hitting the floor.



"That’s unsure at this point, if the bike has been turned on after the fluid loss occurred. The ABS pump initializes when the bike is turned on and any application of the front brake lever activated the pump, drawing fluid (or air, if the reservoir was low due to the fluid loss) from the reservoir to apply pressure to the caliper pistons."


The ABS pump never turned on. I would have clearly heard it. No brake lever was touched during the short period when the key was "ON". The 3 front brake lever squeezes that pumped fluid out were performed with the key out of the bike.

 

[k547]

I've been waiting for a brake system DVD to arrive and at this point squeezing the front brake lever has no effect on either the front or rear wheels.

I have read numerous post about pushing the brake pads apart to do wheel/tire/shock changes etc. and NONE of them mention any problem using the brakes afterwards.
As much as wanting to restore my brakes I'd like to know why this happened.

 

[k547]

Couldn't sleep so being bored I just went back out into the garage and turned the key on waited about 30 seconds and after a few pushes of the brake pedal and squeezing the front brake lever my servo finally energized (it was not turning on prior to this) and and the front lever felt normal after a couple of squeezes. The fluid level in the "Front" portion of the rear mounted reservoir dropped back down to its normal level instead of being over full. I don't know why my first two attempts didn't work but on the third try everything seems to be back to normal.

I was/still am in full agreement with this statement that another forum member made made:
"If you have not opened any line nor run the system with the reservoir empty, there is no need to bleed."

I'm glad it worked out.

 

[k547]

Finally figured out why my brake modulator servo would not energize, it had nothing to do with pushing the front brake pads back. It was just a coincidence that another issue occurred at the same time I had been moving the front pads.
It is the rear brake foot pedal micro switch - it is properly adjusted but has developed an occasional intermittent failure to close the circuit. I'll replace the switch and the brake pedal return spring, both being original circa 2003 parts. Sure had me puzzled.....lol

 

[k547]

The existing rear brake pedal switch looked like someone had partially melted the housing by poking it with something hot. The leaf spring was bent way out which does nothing since the bolt on the foot pedal will just compress it back to the usual position. And there was no discernable motion or "click" detent to the plunger when it was pressed.



The new switch had a movable plunger with an obvious "click" as it moved in and out through it's on/off detent.



All my problems with the brakes went away after installing the new switch.
No issues with the servo not energizing after moving the caliper pistons in and out while installing new front and rear Dunlopad sintered street brake pads.
I've noticed that these brake pads produce significantly less and lighter colored brake dust than the stock factory BMW pads that I removed.
So far they are very quiet.
No complaints about the "feel" or braking action.

 

[Omega Man]

Nice follow up.

OM