As the title reads, I've just rebuilt all of the calipers on my 1985 K100RS.  I also flushed all of the old brake fluid out with new and I do have brakes, but there is still a lot air in the line and I'm having a real problem evacuating it.  I don't have any sophisticated equipment or bleeding tools other than a pump oil can (bought especially for this purpose) filled with brake fluid that I pumped through the system at the bleeder nipple up to the master cylinder reservoir.  What would be the best way to proceed now?  Pump up the brakes and then purge at the bleeder nipple??  These are Brembo single piston calipers.

Thanks in advance for you input.

Reverse flushing through an open bleed nipple can actually drag some air past the loose thread of the nipple.
Your local Vet may have a 100ml syringe that you can use to vacuum bleed it. I got one for $4 a while ago and it is good for all sorts of things including getting extra oil out after an overfill.
The K100 front brakes can be very stubborn at times and at one time I removed the calipers still attached to the lines and put some insertion rubber between the pads so as to get some more movement from the pistons as they returned hoping to push the air back out the top.
I have also levered the pads back into the calipers as far as I could to get a similar effect.
On a car I once owned I put some plastic tube from the wheel cylinder to the top of the M/C and sat in the car  and read a book while pumping the brakes and eventually got the last of the air out.

jumpinjimmy wrote:As the title reads, I've just rebuilt all of the calipers on my 1985 K100RS.  I also flushed all of the old brake fluid out with new and I do have brakes, but there is still a lot air in the line and I'm having a real problem evacuating it.  I don't have any sophisticated equipment or bleeding tools other than a pump oil can (bought especially for this purpose) filled with brake fluid that I pumped through the system at the bleeder nipple up to the master cylinder reservoir.  What would be the best way to proceed now?  Pump up the brakes and then purge at the bleeder nipple??  These are Brembo single piston calipers.

Thanks in advance for you input.

I had the same sort of problem.

Was knocking myself out attempting to fixit.

By accident I discovered (for the FRONT ones) that if I unhooked the pushrod at the master cylinder, held it in while putting it back together, and then bled it up again in the normal way (gravity fed and then plug in a one way brake bleeding valve and then pump it a couple of times) then it came right. Seems the plunger was somehow letting air in there

The only other thing I can suggest is, if you have the old rubber brake lines, they may be TOO old and actually be expanding when you bleed them up. I tried braided lines and , wow, what a difference they make. Not cheap though, about $100 a pop to have them made

"Pump up the brakes and then purge at the bleeder nipple??" Correct

Put a ring spanner on the nipple nut and then place a tube over the bleed nipple and into a container. Pump brake and keep pressure on. Release bleed nipple to release pressure. Close nipple and then release brake leaver. Repeat many times. Watch for air. It can take quite a while and you'll need plenty of fresh brake fluid.
Make sure the reservoir doesn't run out or you'll introduce more air into the system.

DON'T GET BRAKE FLUID ON YOUR PAINT WORK!! Have a wet rag or spray bottle handy so you can clean up immediately.

There are some inexpensive bleed kits available for AU$10 to $20. The best I've seen is one which has a tube with container which you hang somewhere above the nipple so the tube doen't drain and let air back through. I made my own version.
http://www.ebay.com.au/itm/BRAKE-BLEEDING-KIT-NEW-/151128657068

I tried this one without a lot of success...

and then bought this one and it worked perfectly. This is more expensive, but worth every penny.

I just had a look on ebay and saw the purge kit you show here for around 20 euros so I'm going to invest in one and get this sorted out properly.  Thanks for posting that.

Looks like a handy tool and reasonably priced as well. $30 in Australia incl shipping. I'll buy one myself and ditch my old bottle.

I've used the top device in CF's post, had a lot of difficulty with the back brake but the fronts were reasonably straight forward. My K has the front brake line through the headset then splitting in a Y under the headset.

Hey Kaptain, this is what I use. A Victa Oil Removal Kit...from Bunnings, 30 or so dollars. Works on a vacuum. Piece of cake and quick!

blaKey wrote:
Hey Kaptain, this is what I use. A Victa Oil Removal Kit...from Bunnings, 30 or so dollars. Works on a vacuum. Piece of cake and quick!

I like that ingenuity! and the big bottle. I had to pump over a litre thru my rear brake last time. The brakes had been neglected for some time by the PO. It would've been a lot more efficient if I'd used a vacuum system. I'm sold.

I'm thinking also that may be good for removing the dregs from the fuel tank when cleaning it out.

Cheers

G'day KH, had the same problem bleeding the front brakes on the 75. A local motorbike guru said the master cylinder should be at the highest point.???? (WDIK). So turned the handlebars to full left lock and it worked for the 75 anyway. Thats my 2cents worth. Cheers Tom

RicK G wrote:Reverse flushing through an open bleed nipple can actually drag some air past the loose thread of the nipple.

Remove the bleed nipple and wrap some ptfe (plumbers tape) around the thread first helps to eliminate this.

Yes to what the.postman said.

Yes to what Tom said.

If you buy brake fluid that is a different colour to what you are replacing, you'll see it come through the plastic tubing, so you'll know when to stop.

As Tom said, turn the handlebars to the left. The reservoir will be the highest point. But place a rubber band around the grip and the brake lever. Leave it over night and the air/bubbles will migrate up to the reservoir.

the.postman wrote:

RicK G wrote:Reverse flushing through an open bleed nipple can actually drag some air past the loose thread of the nipple.

Remove the bleed nipple and wrap some ptfe (plumbers tape) around the thread first helps to eliminate this.

You gatta be very careful to remove ALL of it coz if it does work its way to a seal it can and often does get under the seal and cause a weep. Any of the hydraulic experts I have ever worked with say don't use it just isnt worth the trouble it can cause.

I have the end off a brake line with a ball flare and nut. Screwed in tight with a piece of plastic tube over it and clamped works well for vacuum bleeding as any air you see can then be safely assumed to have come from the system and not the loose thread.
However what ever you can do to prevent false bubbles is on the right track and the numptie who decided to put that steel crossover tube on the ABS K100s should be condemned to a lifetime of bleeding them. I think he was a sadist.

My K1100 has 2 separate flexible lines from the steel tube where it comes over the top of the radiator and it is much easier, not real sure but I think all the K1100s are like that.

the.postman wrote:

RicK G wrote:Reverse flushing through an open bleed nipple can actually drag some air past the loose thread of the nipple.

Remove the bleed nipple and wrap some ptfe (plumbers tape) around the thread first helps to eliminate this.

A more simple and easy (you don't have to remove the bleed nipple) metod is,
use some brake cylinder mounting grease around the visible bottom part of the bleed nipple.