Ok first off let me give you an idea of my setup. I am trying to bleed the front brake and after about 5 hours I have gotten nowhere. I have blead brakes before so this is not my first time. The banjo bolt on the caliper had been removed so I went out and got brand new crush washers to make sure it was sealing as it should at the caliper. I then positioned the caliper above the master cylinder to help get the bubbles out since they like to rise to the top.

After that I removed the bleed nipple and re-applied teflon tape. And then re-installed it. I then attached my Mityvac to the bleed nipple and pumped it up to 20 in/hg I cracked the nipple open a half of a turn and the bleeding process has began.

I took extra special care to make sure the level in the master cylinder has not dropped below half full. After pulling about a quart of brake fluid through the lines with the Mityvac I sealing everything up and the lever pulls straight back to the bars as if I had not blead the brakes at all. Obviously there is still air in the system but how the hell is it getting in there. :foul: :foul:

I am beyond pissed off at this bike right now. Does anybody have any idea where I could be pulling air into the system? Is this an indication that the master cylinder is shot? If so can it be rebuilt or do I need to buy a new one?

Bad master cylinder?

Did you try just bleeding it the manual way?

biggziff said:

Yes I did

You tried pushing the pistons back to squeeze air out?

There should be no Teflon tape on the bleeder screw. Master cylinder should be higher than the caliper. Bleeder screw should be at the highest point on the caliper but below the MC.

Try removing the line from the MC and carefully pump the clutch cover the out let with a rag to catch any fluid. Better yet take the MC off and it outside and don't point it at anything you love. Remember brake fluid will remove paint quickly. If fluid comes out, not in a drip but in a stream the MC should be good.

Bolt everything back on the bike and try again.

Pedroski said:

Only when I first put the caliper on in order to get the disk in

tedhone said:

I tried doing it the conventional way first with the caliper attached to the wheel and had the same problems so I tried this way with the caliper above the master cylinder.

carters2 said:

Carters2, is it a Brembo caliper? If so, then this worked perfectly for me yesterday, starting with a completely empty system. With caliper on bike, new pads and pistons pushed right back, I remove bleed nipple and using a small syringe I injected brake fluid straight into the caliper. This filled the caliper right up to the bleed nipple and ensured there was no air in there. I refitted bleed nipple but left it opened half a turn. Next I removed cover from master cylinder and filled with fluid. I pulled the brake line down so that the master cylinder was the highest point. When squeezing the lever slightly on and off air bubbles came out from the hole in the bottom of the master cylinder. I kept doing this for a few minutes and eventually fluid came out of the bleed nipple as the air was displaced. Tightened bleed nipple, topped up master cylinder, and pumped lever a couple of times. Pressure built up and I cracked bleed nipple open as I squeezed lever, then did nipple up again just before lever reached full travel. Repeated this a couple of times to make sure fluid squirted out of nipple when lever pulled and nipple cracked open. All is good. Very good. And should be same for other calipers.

Pete

Yes, keep the caliper below the m-cylinder (bolted onto the fork). Make sure you don't have a loop of brake line going above the m-cylinder before it goes down to the caliper, as this I've heard, can trap a bubble of air that won't come out. Set up like that it should'nt take but a couple of vacuum pulls with the Mity Vac to do the trick.
Changed out all the fluid in the systems on both ends of my KDX, took about 15 mins and a cup of brake fluid on each end from start to finish.
If you do all of the above and it still doesn't work, I'd be looking real close at that m-cylinder.

I start with a mityvac, but finish up the conventional way (squeeze brake lever, open bleed screw and then tighten bleed screw, release brake lever and repeat). After that, I rubber band the brake lever fully actuated, and leave it that way over night. That seems to knock all the bubbles free and makes it rise to the top.

I feel your pain, now spend 12.00 on a set of speed bleeders and be done with it. It is that easy, I have beat my head against the wall trying to bleed crf brakes but no more.

I've been told these work much better than the vacuum systems. I have a MityVac and could never get it to work on any vehicle.

This system shown below makes a lot more sense as you're pushing fluid and air back UP to the MC. Air wants to rise anyway so.....