no brake pressure

[Parr8hed]

I am about to throw these brakes and everything attatched into the Ohio river! I have the new rebuild kit in the master cylinder. When I have it off of the bike I have brake fluid oozing out as I pump the lever. If I put my finger over the opening I can build up air pressure, I can hear it escape as I lift my finger. When I pull my finger away a small amnt. of brake fluid comes out.

When the m/c is back on the bike, I can't build up any pressure at all. I have tried everything on the bleeding tips except for getting an old oil can and reverse bleeding that way, not sure where to find one or I would try that too. I have been outside pumping on the brake lever for over an hour to try and build up some kind of pressure to bleed the brakes with, but not any more now than when I started!

Anyone want to but this bike? (just joking, well maybe.....)

Travis

[Parr8hed]

I went and got one of the vacum brake bleeders from sears. I bled out a bunch of bubbles, went through about 2 brake line lenghts of clear new brake fluid in the tubes. I am pretty sure that there are no bubbles in there. I still have no pressure! I am perplexed.

[rneal55555]

I had the same thing on mine, although none of the components were rebuilt. I couldn't find on the day I went looking one of the handheld vacuum bleeders. So I resorted to using the vacuum oil changer I have for my boat it moved fluid so fast I really had to watch they level it was almost a 2 man job. I sucked almost a pint of fluid through the system and they worked fine after that.

You might try just pulling more fluid through try and get a helper to keep the level topped of and tap on the master cylinder while your doing it to help dislodge any trapped air bubbles.

If that doesn't work you might have something not right in the master cylinder There's a post in the tech tips about the rubber cup getting reversed if its allowed to over travel you might want to check that out.

Good news is by the time you get it figured out you'll be an expert the next time.

[skids]

Keep in mind that I have not tried this, but someone once posted that if you tie the brake handle and leave it that way at least 24 hrs, it will allow bubbles to pass through the master cylinder and out of the system.

Originally posted by Parr8hed
I went and got one of the vacum brake bleeders from sears. I bled out a bunch of bubbles, went through about 2 brake line lenghts of clear new brake fluid in the tubes. I am pretty sure that there are no bubbles in there. I still have no pressure! I am perplexed.

[Parr8hed]

We had the rubber thing on backwards on the piston. I reversed it just like the tech tip says and put it all back together. I then bled the lines for about 45 in on each side getting a ton of air bubbles out. Everything felt right. When I put the lid back on the reservoir I still had no pressure. I pumped the brake lever for about 5 min and still no change in pressure. I am going to leave the lever taped back until the morning and try some more.

When you bleed with an external device and you are sure that you have out all of the bubbles, how long does it usually take for the lever to build up pressure? I am XStremely frustrated right now. I am going to have a cold beer and go to sleep.

Travis

[knewsom]

Bleedin' HELL

Dude, did you ever get this fixed?? I'm having a similar problem - I can't even build up enough pressure to force a drop out of the bleeders! If you did, please share your secrets, because it's been MONTHS since I got this bike, and I STILL HAVENT GOTTEN TO RIDE IT.


hope to hear from you soon on this one - I've been outside in the sun squeezing on that thing all dern day, and I'm about as frustrated as you were in your last post.


*sigh*

-Kris

[greywolfe555]

you mite try blowing air threw the brake line from the caliper end.but first disconect the line at the master cylinder .this should get all the crap out of the lines so you can properly bleed them good luck

[knewsom]

Tried something similar... put the top end into an old vitamin jar full or brake fluid, then hooked up my brand new vacum pump to the bottom one...

on the right side, things seemed to work just dandy.


...but on the left, alls I got was bubbles.



I think I have a leaky seal in my left caliper.

[planedick]

Same problem...

I had that problem when I did my brakes and found that if I loosen the fitting just behind the master cylinder where the hose attaches, you can get it "primed" so to speak, then squeezing the lever will make fluid flow and then you can then tighten it up again and you can build pressure to bleed the brakes.

[cafexs1100]

seals

Ive had this same problem where the master cyclinder itself was not sealing correctly when the cap was on and air was breathing back and forth through the bad plastic insert, hence no pressure.

Ive also had the problem where the pistons were scratched too much or were not cleaned enough and either stuck completely or leaked badly or breathed. Put your finger next to the pad, not in it!, and squeeze the brake, you should feel it move a little - if it doesn't, then its sticking or not getting pressure.

[prometheus578]

"Ok, here's the deal, Parrot Head"

But let me clear something up, first.

where the master cyclinder itself was not sealing correctly when the cap was on and air was breathing back and forth through the bad plastic insert, hence no pressure.

The master area in question just holds the fluid. Pressure is only built up in the inch or so of the piston/cylinder area. Air is supposed to be able to enter the resevoir(sp) to replace the displaced fluid. The rubber boot thing telescopes/expands to take up the air space so that air can't inadvertantly get sucked down to the piston area.
Alright... let the bleeding begin!
(And it's gonna get messy)
Fill the master mit der fluid. Loosen the fitting where the master meets the brake hose. Pump the master a few and then crack the fitting a little. Some air and some fluid should escape. Pump and hold the lever back, open the fitting, close the fitting, release lever and do again. Do this several times. That should clear that area.
Now... there's still some air in the piston area. Remove some of the brake fluid from the master, but keep enough in it to safely cover the two holes at the bottom(splooge holes). Turn the handle bars to the left. The master should now be angled downward. SLOWLY pump the lever. You should now see bubbles from the air that was trapped between the fitting and the front of the plunger bubble out of the holes. Do this fer a spell.
Turn the bars to the right and do agi'n. Not you should see bubbles from the air that was trapped on the right side o'
the piston. Go back and forth till no more bubbles.
Also, be advised, that the brake line junction on the lower fork clamp can also hold trapped air depending on it's orientation. As you move the bars left and right and it's angle changes, tap it with a wrench a few times to dislodge any bubbles living there, too.
Good, now the master is bled, and you can proceed with bleeding as normal.
You know the drill, so no need to go into it now.

I went and got one of the vacum brake bleeders from sears. I bled out a bunch of bubbles, went through about 2 brake line lenghts of clear new brake fluid in the tubes

Many times the bubbles you are seeing in the clear hose are coming from leaks where the vacuum hose connects to the bleeder nipple. This is not air trapped in the line. Vacuum bleeding is fast and easy, like my last girlfriend.
Ummm... what else?
The oil can can be bought from any hardware store, or Harbor Fright. Fill the can mit der fluid, hook a hose to it. Pump the can to clear the air from the line and place it over the caliper bled nipple. Force brake fluid up the lines backwards to push the bubbles up and out through the master.
The rubber band trick works as a last resort, but is effective when one gets frustrated and it does get results. Turn the bars to the left so the master slants down. Rubberband or tape the lever back and let it set. You may also want to tap the brake lines occasionally to help dislodge any stubborn bubbles. With the lever taped, the pistion is forward, which sometimes helps the bubbles move up and out.
My thoughts on what this technique does: By leaving the lever back, you have pressurized the system to some degree. This compresses the air bubbles a little, allowing them to move up the line a little easier. They float up to the master, and can then be removed by turning the bars left and right.
Firing up the bike... the vibration also helps jiggle the little SOBs and send them on their way.

[cafexs1100]

Actually, I forgot to mention that on the first pull of the brake I had no pressure, on the 2nd pull I had pressure. It was a CBR 600 f4, and the pressure was missing after the wheel rolled. Roll, hit the brake, no pressure, hit it again, pressure. And yes it was the top seal in the reservoir, you could see the bubbles coming out of the cap - one replaced it worked fine.
-- I dont make the rules, unless I have a hammer.

[John]

One thing to be aware of is the O ring that seals the reservior to the master cylinder, They can get a flat side on them and leak.

[knewsom]

wow - some awesome tips here, sadly I've tried most already.... to no avail

Next step is to do a reverse bleed with an oil can. I've already gone through 40 oz of brake fluid trying to get this to work!!! MC should be fine - it's brand new from partsnmore.

If I still can't get 'er to work, I may have to bite the bullet and take it to the Yamaha dealership and say FIX IT!

Seriously, I'm at the point where if I don't get to ride this thing SOON, I'm gonna have to take some drastic measures.

[prometheus578]

It was a CBR 600 f4

I know not of a CBR600f4, so shall remain mute.