Brake Bleeding... What am I doing wrong?

[def38]

I'll respectfully disagree. I've replaced the master cylinder on my oilhead with ABS. I completely drained the system, replaced it and filled it up again. I use a mityvac: handheld. It worked fine as it has on my TDI VW, my Montero and every other vehicle I've owned over the last 10+ years.

Now the oilhead did take some tapping here and there, cracking the banjo bolt at the master cylinder, but with patience and feel, it was back to normal inside of an hour.

Please keep in mind that I'm not disagreeing that you had trouble. I've never done a K75. I'm disagreeing that every vehicle with ABS is difficult.

If a mechanic at the BMW shop can do it, so can you. The difference is, you need a reference to refer to....like the BMW Repair CD Manual or some other reliable reference.

There is NO MAGIC to maintaining and repairing these motorcycles we ride...mere mortal man can fix it......so can you!

[Sport-Touring]

[JimWilliamson]

Only problem is you have to have a resevoir cap to butcher, drill it and thread a bleeder to it with a tube to a jar so you don't get fluid everywhere.

For those with rectangular metal tops for the master cylinders (instead of plastic screw on caps) you can made a similar thing with some rubber gasket material and some 1/4" thick clear plastic. Drill two holes for some hardware store / longer screws. One larger hole in the middle for a hose connection. Cut the center out of the gasket (for the tube connection) and to see inside of the reservoir. Pix available if interested.

[RodRides]

Motorcycle brake bleeding 101.  See video

https://youtu.be/m2Gu0ExObrw

[roger wilco]

I have spent way too many hours in my life trying to bleed the last of the air out of motorcyle brake lines so that the brake levers do not remain ‘spongy’.
My most recent attempts at bleeding brakes have resulted in consistant successes and so I want to share what I do so that others might try and hopefully find a solution to this frustrating problem.

What I do is bleed the brakes in the usual manner. That is,  using a wrench to quarter turn the bleed nipple allowing the brakes to bleed while gently depressing the brake lever, then retightening the nipple prior to letting the brake lever off again while taking care that brake fluid in the resevoir does not run out.
The important thing here is to start bleeding the caliper – nipple which is  furtherest away in the line from the fluid resevoir .
Then in the case of dual disc brakes, proceed to the caliper – nipple which is next closest to the resevoir.
This process will get rid of most of the air and sometimes all of it but this has been rare in my experience. Too often the brakes remain way too spongy for my liking.  I have pretty much the same results using the vaccum pump and catch canister method.

To get the remaining sponginess out of the brakes I do the following
With the brakes fully attached to the rotors, I gently pry the brake pads away from the rotor/disc with  large flat blade screwdrivers, taking care not to gouge the pad surfaces, so that reverse of the disc pads pushe the slave pistons back into the caliper housing- as far as it/they will go.
This will force any air still caught in slave piston to be displaced back up into the line and ultimately back into the resevoir.  I believe such air is hard to get out with the intitial bleed.
I find it is also a good idea to initially slowly move the brake lever intialy just a couple of mm after feel  uptake, as at this point, the fluid (and air) can  escape into the resevoir. As the lever becomes further depressed beyond those intial couple of mm, this port in the master cylinder will shut off access back into the resevoir as it then proceeds to  force fluid on down the brake towards the slave cylinder. You will need to gently  pump the brake repeatadly until the brake starts to firm up – as the pads meet with the rotor -disc. As before, start the process with that slave cylinder  furtherest away from the resevoir then repeat the whole proceess to the next closest slave cylinder to the resevoir.
 After completing this process, the brakes should then feel very firm and you’re ready to go.