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Brake bleeding


Sandbag

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Need a little help, I put on new front pads today & after I had everything together I went to pump up the brakes & they were mush. So I pulled out the might vac & after about 30 minutes I came to the conclusion that me bleeders were clogged. After removing each one blowing them out with the air hose I was able to bleed the 2 front calipers but the rear will not bleed. The bleeder is not clogged & I even tried without the bleeder in & nothing. I have bleed the brakes before with no problems. Any ideas what may be the issue?

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Assuming your brakes are still in the original linked configuration, most of the bleeding is done from the rear fluid reservoir. You might take a look at this thread on another Blackbird web site which distills the process somewhat:

Bleeding the Bird on cbrxx.com

I found it necessary to gently pump the brake pedal for the rear caliper center bleeder while pulling a vacuum with the Mityvac.

If you're familiar with the process and it still didn't work, I've got no idea what happened.

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Assuming your brakes are still in the original linked configuration, most of the bleeding is done from the rear fluid reservoir. You might take a look at this thread on another Blackbird web site which distills the process somewhat:

Bleeding the Bird on cbrxx.com

I found it necessary to gently pump the brake pedal for the rear caliper center bleeder while pulling a vacuum with the Mityvac.

If you're familiar with the process and it still didn't work, I've got no idea what happened.

That's what I was looking for, I will try it this evening when I get home. Thanks for the info.

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Don't forget to have someone bleed the center piston on the rear caliper by pulling up and pumping the left front caliper which is attached to a brake cylinder. By the same token, the rear brake M/C also sends fluid to the front calipers that need to be bled as well.

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2 pints of dot 4 later I finally got all the air out of the lines. What a PITA. Thanks to all who gave constructive help.

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OK so I'm still screwed. Using the rear pedal I have great front breaks, but with the lever I have poor front breaks. After a few hours of reflection I remember that I never saw the front MC fluid drop as I was doing the rear outer (rear) bleeder. It would only pull from the rear MC if I pumped the rear pedal. Why can't I get the line from the front to the rear to bleed properly?

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That's because the rear brakes, and the rear-to-front linked brake circuits, only draw fluid from the rear master cylinder reservoir. The only link the front brakes have to the rear is mechanical via the little master cylinder rod attached to the left front caliper bracket (the one that moves when the front brakes are applied while the front wheel is in motion). There is no hydraulic fluid path from the front master cylinder to the rear caliper.

This drawing from section 15 of the CBR1100XX Shop Manual shows the front brake fluid paths:

post-1023-1276230484.jpg

This drawing shows the rear brake fluid paths which does have a fluid path from the rear master cylinder to the front calipers:

post-1023-1276230506.jpg

So, bleeding both the left and right front caliper outter (the ones on top) nipples should draw fluid from the front brake reservoir, and that is where your front hand brake lever does it's work. It sounds like you either still have air in those lines or caliper piston bores, or your front master cylinder is not functioning properly, either due to air in there, or bad seals.

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Assuming your brakes are still in the original linked configuration, most of the bleeding is done from the rear fluid reservoir.

Yes, the XX with linked brakes (didn't learn this until recently) is only linked rear to front. The front brake only works on the front wheel. The rear does both the rear and the front.

Frustrating work....especially if your lines are empty. I had to suck on the bleeder line to get the master cylinders to start pumping.

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Two words:

DE-LINK!

Saves a couple pounds of weight and a whole lotta headaches. All you need to buy is the two-line kit from Galfer.

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I have bleed my ars off & I'm still not getting proper front with the lever. I had cracked the banjo at the MC (under pressure) & both outer bleeders, used the mighty vac & it still is mush. All I did was install new pads & I had to push the pistons back in too allow the new pads to fit. Then when I went to pump up the front before taking the bike off the lift nothing. I pulled out my mighty vac & accidentally ran the MC dry. That certainly shouldn't have damaged anything to cause this. :icon_wall:

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I pulled out my mighty vac & accidentally ran the MC dry.

It is a real pain to get the air out once you let it in. As you are trying to bleed with the M/C top on, move the bars from one side to the other to give the trapped air a chance to move.

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Anyone know how that piston on the left side front caliper is bled?

Looking at the lines it looks like a brake line goes to the top, but that's it. Since I replaced all my lines, I presume that following the bleeding instructions got all the air out, but this presumes that fluid flows from a master cylinder to a bleed nipple. There's no bleed nipple on this piston, so how does the air get out?

:icon_confused:

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Anyone know how that piston on the left side front caliper is bled?

There is an input brake line on the side of the linked left front master cylinder and an output line on the top. I think the fluid is circulated through the cylinder during the rear caliper outter nipple bleeding procedure, while the piston is in the relaxed state. When front wheel brake motion activates the piston, it closes the input port to apply pressure to the rear caliper, just as the front handlebar master cylinder piston closes it's reservoir port to apply pressure to the front calipers.

Sandbag, it sounds like you actually lost your front brakes by pushing in the pistons to accomodate the new front pads before doing any bleeding. Did they not pump up any at all after the pad install, or were they just soft? Did you check for fluid loss at the front calipers? If the piston bores were very dirty or corroded, you may be getting air in there as you try to pull fluid with your Mityvac. Do you pull clean fluid from the outter bleeders, or is the fluid foamy with air bubbles?

Can you get any pressure at all from the brake lever? If you pump the brake lever 5-10 times, then while holding it down, crack a bleeder, does fluid come out the bleeder? If fluid comes out very fast, you probably still have an air bubble in the system that you are compressing instead of moving pistons against the pads. The T-blocks and the cross-over line would be the only other place besides the caliper piston bores that might collect air.

If pumping gets you no pressure, there's always the possibility that pushing the caliper pistons in caused trash to be lodged in the master cylinder piston seals, causing you to not be able to get any pressure from the master cylinder itself. That would require taking the master cylinder apart and at least cleaning it all up, possibly requiring a new seal kit.

I haven't had to deal with your situation on a Blackbird, so perhaps someone else who has had similar problems with the front brakes will chime in.

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Anyone know how that piston on the left side front caliper is bled?

There is an input brake line on the side of the linked left front master cylinder and an output line on the top. I think the fluid is circulated through the cylinder during the rear caliper outter nipple bleeding procedure, while the piston is in the relaxed state. When front wheel brake motion activates the piston, it closes the input port to apply pressure to the rear caliper, just as the front handlebar master cylinder piston closes it's reservoir port to apply pressure to the front calipers.

Sorry if I sound stupid, but are you saying that the piston I'm looking at has two lines? One on the side (I seem to not be seeing) and one on top? I see one on the side (facing the fork) but that bolt has two lines...one going up and one going down to the caliper. Is that the one you're talking about? Side (front) feeds in and top feeds out? How do you bleed that piston or is it more of a pass-through line so bleeding the rear automatically flushes air out a rear nipple once it runs the whole loop?

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Anyone know how that piston on the left side front caliper is bled?

There is an input brake line on the side of the linked left front master cylinder and an output line on the top. I think the fluid is circulated through the cylinder during the rear caliper outter nipple bleeding procedure, while the piston is in the relaxed state. When front wheel brake motion activates the piston, it closes the input port to apply pressure to the rear caliper, just as the front handlebar master cylinder piston closes it's reservoir port to apply pressure to the front calipers.

Sorry if I sound stupid, but are you saying that the piston I'm looking at has two lines? One on the side (I seem to not be seeing) and one on top? I see one on the side (facing the fork) but that bolt has two lines...one going up and one going down to the caliper. Is that the one you're talking about? Side (front) feeds in and top feeds out? How do you bleed that piston or is it more of a pass-through line so bleeding the rear automatically flushes air out a rear nipple once it runs the whole loop?

Yes, the line going to the center piston (fed by the rear master cylinder reservoir) on the left front caliper passes in and out of a "T" that serves as an input reservoir for the link secondary master cylinder. The piston bore in the link secondary master cylinder is bled by fluid passing through it, out the top, on through the Proportional Control Valve to the outter pistons on the rear caliper. This can happen as long as the secondary master cylinder link rod to the left front caliper is at rest.

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Anyone know how that piston on the left side front caliper is bled?

Sandbag, it sounds like you actually lost your front brakes by pushing in the pistons to accomodate the new front pads before doing any bleeding. Did they not pump up any at all after the pad install, or were they just soft? Did you check for fluid loss at the front calipers? If the piston bores were very dirty or corroded, you may be getting air in there as you try to pull fluid with your Mityvac. Do you pull clean fluid from the outter bleeders, or is the fluid foamy with air bubbles?

Can you get any pressure at all from the brake lever? If you pump the brake lever 5-10 times, then while holding it down, crack a bleeder, does fluid come out the bleeder? If fluid comes out very fast, you probably still have an air bubble in the system that you are compressing instead of moving pistons against the pads. The T-blocks and the cross-over line would be the only other place besides the caliper piston bores that might collect air.

If pumping gets you no pressure, there's always the possibility that pushing the caliper pistons in caused trash to be lodged in the master cylinder piston seals, causing you to not be able to get any pressure from the master cylinder itself. That would require taking the master cylinder apart and at least cleaning it all up, possibly requiring a new seal kit.

I haven't had to deal with your situation on a Blackbird, so perhaps someone else who has had similar problems with the front brakes will chime in.

I can pump the lever till I'm blue in the face & I can't get any pressure to account for anything. I took the MC apart & it looks fine I didn't see any trash at all. Reassembled went through the entire front bleeding procedure & still nothing. Assuming that the front lever isn't connected to the rear (fluid wise) there is no reason to bleed the rear, correct?

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I can pump the lever till I'm blue in the face & I can't get any pressure to account for anything. I took the MC apart & it looks fine I didn't see any trash at all. Reassembled went through the entire front bleeding procedure & still nothing. Assuming that the front lever isn't connected to the rear (fluid wise) there is no reason to bleed the rear, correct?

No, unless the front calipers have been monkeyed with, (i.e. in some de-linking procedures, new passages are drilled in the caliper castings between the center piston bores and the outer piston bores), the front master cylinder only operates on the two outer caliper pistons (and the outer bleeder) on each side of the front wheel.

This is pretty late in the game, but exactly what model Blackbird do you have? All my documentation and experience relates to the late model, 1999 and later, LBS setup.

Using a Mityvac usually makes bleeding easier, but are you able to move any fluid using the old classic method of filling the reservoir, pumping the master cylinder lever, holding the lever down, then cracking a bleeder with a line going into a waste fluid container, closing the bleeder, releasing the lever, re-filling the reservoir, pumping the lever again, and repeating the cycle? This works better as a two-man operation. If this works to move fluid from the M/C reservoir to the waste container, then you must have air either in the lines or the piston bores.

If this doesn't work, it sounds like something is still wrong with your master cylinder.

Also, to verify, this is what I am calling the "outer (or misspelling as outter) bleeder":

post-1023-1276574083.jpg

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No, unless the front calipers have been monkeyed with, (i.e. in some de-linking procedures, new passages are drilled in the caliper castings between the center piston bores and the outer piston bores), the front master cylinder only operates on the two outer caliper pistons (and the outer bleeder) on each side of the front wheel.

This is pretty late in the game, but exactly what model Blackbird do you have? All my documentation and experience relates to the late model, 1999 and later, LBS setup.

Using a Mityvac usually makes bleeding easier, but are you able to move any fluid using the old classic method of filling the reservoir, pumping the master cylinder lever, holding the lever down, then cracking a bleeder with a line going into a waste fluid container, closing the bleeder, releasing the lever, re-filling the reservoir, pumping the lever again, and repeating the cycle? This works better as a two-man operation. If this works to move fluid from the M/C reservoir to the waste container, then you must have air either in the lines or the piston bores.

If this doesn't work, it sounds like something is still wrong with your master cylinder.

Also, to verify, this is what I am calling the "outer (or misspelling as outter) bleeder":

Mine is an 02 & yes we are talking about the same outer bleeder. I have tried the old school pump & crack but I get very little fluid to flow. I did notice that when I took the MC off, after I put it back together I put my finger over the output & on the first pump there was significant pressure, on the next pump just slight pressure. I'm starting to wonder if there is a tiny tear or defect in one of the seals allowing fluid to slip by.

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Your original problem points to the master cylinder, because it should have been able to pump the pistons back out, after you originally changed pads, with two or three pumps of the lever.

If pushing the pistons in to insert the pads ruined those piston seals, the master cylinder should have pumped fluid out around them. If the pistons jammed, your brake lever should have been hard and high, not mushy.

When you originally tried to bleed the front brakes, you said you thought your bleeders were stopped up. If you were trying to bleed the outer bleeders, that sounds like the master cylinder piston was down in it's bore enough to cover the pressure weep hole, not allowing any fluid to be drawn from the reservoir.

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Fixxed :icon_evilgrin: I took the front wheel back off, pulled the pads, & pumped the MC & the pistons one at a time extended. I then pushed the pistons back in one at a time & set the pads back in. Pumped the MC & I suddenly had full lever :icon_think: . After reassembling the front end I still had full lever. Checked the MC & it was 3/4 low. Filled it back up & I'm back in business. I'm not sure where the bubble was or how it came out but I'm back in business.

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Fixxed :icon_evilgrin: I took the front wheel back off, pulled the pads, & pumped the MC & the pistons one at a time extended. I then pushed the pistons back in one at a time & set the pads back in. Pumped the MC & I suddenly had full lever :icon_think: . After reassembling the front end I still had full lever. Checked the MC & it was 3/4 low. Filled it back up & I'm back in business. I'm not sure where the bubble was or how it came out but I'm back in business.

Congrats! Glad you got it working.

Now you know why they say to never let the reservoir run dry while you are bleeding the brakes.

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