Now I'm trying to bleed them, but having some trouble. I just filled the MC with fluid and started to pump the brake lever with one bleeding nipple open. Doesn't seem to be working. Do I have to open both nipples? Should I get a syringe and push the fluid up from the caliper into the MC?
Any suggestions on best method(s) after a rebuild?
'78 R100/7 '69 R69S '52 R25/2
'78 R100/7 '69 R69S '52 R25/2
Since the bleeder valves are a straight thread there is air that comes thru as bubbles in the vacuum line. Not to worry, the air can't get into the caliper with vacuum pulling it through.
I have an R90/6 w/dual ATE calipers, splitter under tank and 13mm handlebar M/C.
I flush the fluid through both vehicles every year using this setup.
OKAY, did you change the pads? On the ATE calipers there is a cam system which needs to be adjusted to properly align the pads to the rotor. A mis alignment of the pads will give a poor brake feel. If you didn't change the pads I would still give them a check for alignment and wear, they don't wear evenly.
To bleed, pump the lever a few times then hold it with pressure on it and quickly pop open the bleeder nipple, you should get a clear stream of fluid once the air is all out. Don't keep the nipple open too long and don't pump the lever while it is open or you could get air back into the system. As mentioned a vacuum system works darn well if you have one. Unlike the rear brake on my RS, there is no spot I can think of that would trap air.
Now, last thing, and I just found this on a fellow's bike I was helping him with, is the cable from the handlebar lever to the under tank master cylinder. On my friend's bike we knew we had all the air out of the system and the brake pads properly aligned still the lever went to the handle bar. Cables stretch over time and all we did was adjust the brake cable and that solved our problem. So, check for a worn out of adjustment brake cable.
Hope this helps good luck, St.
There are places for air bubbles to hide in any brake system. Tom Cutter (http://rubberchickenracinggarage.com) has mentioned that an air bubble can be trapped at the front of the M/C bore. He has had to tip the M/C vertically and used a syringe to expel the bubble. It sounds messy, but it worked.
I believe there are off-the-shelf vacuum bleeders like the Air Zapper Brake Bleeder that Brook Reams uses.
Still, like I said, there are other things on the system which can cause a wonky brake feel. BMW made the right choice in going to the handlebar MC and Brembos. Unfortunately, unless we spend money to covert or redesign the system we have, we are stuck with it and the pain of maintaining it. Not that the Brembo system is without it problems bleeding as well. Try bleeding the rear brakes on a 78 RS. St.
The bleed nipple needs to be closed when squeezing the brake lever, then opened, the bleed nipple then is closed before releasing the brake lever, otherwise air just gets sucked back in. So: squeeze lever, open nipple, lever goes to the bar and hold, close nipple, release lever. You might need a helper. Then with the nipple closed, pump the lever a few times, add fluid if appropriate and then repeat the cycle until no more air comes out. With two calipers you’ll need to do that on both sides.
The vacuum techniques work well too, I use a vacuum set up, but after the vacuum bleed I finish off with one or two final strokes as discussed above.