K75 ABS Brake Bleed Issue

[rocketbrick]

Hey gang, long time no see!

I picked up a 1993 K75S with ABS last month.

 I replaced the front master cylinder, which seems to seal and open correctly. The problem: I'm not getting any fluid out of the ABS module, and I'm barely getting any out at the caliper. I tried a motive vacuum bleeder, hand bleeding, really everything. The brake lever is solid, has a really hard feel.

There were maybe around 3 instances of fluid spitting out at the caliper, but the fluid stopped flowing and the brakes still aren't activating. I did push the front pistons back into the calipers.

Can anyone tell me what I'm doing wrong? I've exhausted nearly all forum posts and I can't find a solution that fits my exact situation

[Laitch]

The interiors of rubber lines in the brake assembly could be collapsed or clogged from lack of maintenance.

[rocketbrick]

Gotcha - would you recommend running new ABS line? Never had to do that before, I assume just unplug all rubber hoses and replace. Hit the inside of the front splitter with brake cleaner while I’m at it

[Laitch]

I suggesting that you check the rubber lines and see what's what with them first.

[The Mighty Gryphon]

DSCN3047.JPG (51.83 kB . 670x576 - viewed 323 times)I can't remember the bike I took this fitting off of.


DSCN3050.JPG (26.65 kB . 540x576 - viewed 326 times)
DSCN3052.JPG (32.52 kB . 439x576 - viewed 350 times)

[frankenduck]

If you plan to replace the brake lines then I recommend (and use myself) stainless lines from Motobins in the UK. Price and shipping are reasonable and only takes a week or so to get to the US.

You can usually tell if a brake line is bad by trying to blow air through it. What happens with old K brake lines is that the interior of the the brake line breaks down and clogs it. See TMG's pics above.

[rocketbrick]

Got it - thanks guys. I’ll drain the MC and pop the lines off, shouldn’t be too hard!

Frankenduck, stainless lines will work with the ABS system I assume?

[frankenduck]

SS lines are fine for ABS systems. ABS or not, braided SS lines are better because they do not expand as much under pressure (if at all) as rubber lines. Therefore you get more/better braking for a given effort at the brake lever or pedal.

[rocketbrick]

I might just go SS anyway for that very reason, then.

There's no way to "save" a clogged brake line, right? I'd like to keep them as spares but it doesn't even seem like it'd be worth it

[frankenduck]

A clogged brake is garbage. Toss it.

Brakes are kind of important to safety. Not a good area to skimp.

[rocketbrick]

Just a tad bit important ;)

[rocketbrick]

SS lines are fine for ABS systems. ABS or not, braided SS lines are better because they do not expand as much under pressure (if at all) as rubber lines. Therefore you get more/better braking for a given effort at the brake lever or pedal.

I just bought the motobins front hose kit. The back brake works fine, so I'm going to take care of that one after I fix the front one up. Also, bought two caliper rebuild kits and new pads. Gotta make sure I stop when I need to ;)

[Ingo]

Many moons ago I bought a used 550 Yamaha with front brakes inop. What an experience! 
My breaking is probably 98 % on the front wheel, the rear is for pushing the bike forward and is wearing accordingly.
 Braking on the front at least evens out the front/rear wear a LITTLE bit...

[frankenduck]

I rode my K1100RS on a silt road in The Sierras once while exploring. The ABS made it so that I had NO brakes and could only slow by engine braking. Riding a motorcycle without any brakes was an interesting experience.

[stokester]

I've used Spiegler lines in my K and R bikes.
https://spieglerusa.com/brakes/brake-lines-accessories-tools/cycle-brake-line-kits.html

[Laitch]

I rode my K1100RS on a silt road in The Sierras once while exploring. The ABS made it so that I had NO brakes and could only slow by engine braking. Riding a motorcycle without any brakes was an interesting experience.

Here's the classic video example of that condition.

[frankenduck]

It was level for the first mile or so. Then I started going up a bumpy little hill. Decided being solo in the woods was not a good place to test my luck. I stopped to back down the hill and turn around but the ABS "worked" so I had no brakes to slow my descent. <panic>  I quickly turned the bike off which killed power to the ABS so I did get enough braking back to do a controlled descent and avoid a bike nap.

[Laitch]

I quickly turned the bike off which killed power to the ABS so I did get enough braking back to do a controlled descent and avoid a bike nap.

Quick thinking! The rider in the video could have used that epiphany. Maybe it'll be useful in the future for somebody who reads this now.

[Past-my-Prime]

While well aware that we’ve long ago left the original poster’s question, dare I ask if we can turn the ABS off on these bikes? The “ABS” button - is that only to stop the flashing when there’s a fault code, or does it also (if temporarily) turn off ABS?

[Laitch]

The “ABS” button - is that only to stop the flashing when there’s a fault code, or does it also (if temporarily) turn off ABS?

The ABS button temporarily stops the flashing when a fault is found, but flashing will resume until the button is pressed again, and so on until the fault is corrected. There is no dedicated shut-off switch for the ABS system. If a fault code is registered, the ABS shuts off automatically.

[rocketbrick]

I can see we've been having a bit of fun with the thread 

So, I got the hoses from motobins along with front brake caliper rebuild kits and some brake pads. I ordered the front brake kit and only one of the lines is the correct type (needed both to have at least one banjo fitting but only one does). I'm sorting that out now!

In the meantime, does anyone have any tips on how to crack open the brake line from the ABS modulator under the headlight/fairing to the caliper?

[Laitch]

does anyone have any tips on how to crack open the brake line from the ABS modulator under the headlight/fairing to the caliper?

By brake line do you mean the bleeder bolt? The modulator bleeder bolt is what's opened.

[rocketbrick]

Nope - I mean the coupler of the brake line from modulator to caliper. I’m replacing the brake lines, haven’t had to do any kind of work with these types of couplers before. Sprayed PB and hoping it’s enough!

[Laitch]

I get now! You're trying to loosen them.

[Laitch]

  What could be helpful on this occasion is a Clymer manual. Attached is a page from it with instructions and a page with an illustration. Ignore recommendations involving BMW minions.