Forever Bleeding (brakes)

[Guest Bigin]

Played with this long enough, need new ideas.

 

My rear brake, and of course the left front on the 89 VR, has never been without air in the system, has always been mushy and requires massive pressure to stop aggressively. Luckily have large foot and weigh 280, so I get by but enough is enough.

 

Everything has been rebuilt with exception of calipers, but still has original lines.

 

Bleeding, cant count how many times now, over the last couple years with a vacuum bleeder, at all 3 points in the system and in recomended sequence, and my own random sequence over time, always yields small amount of air in the sytem at the rear caliper, and a greater amount at the steering bleeder.

 

The pedal feels firmer but after a few test stops is back to where it was before the bleed, indicating to me its pulling air.

 

Have made some progress though as the front no longer pulses since the last bleed but still too much pedal travel, too mushy and cannot approach locking rear wheel, which it should be able to if needed.

 

I know I could replace the lines, not cheap, rebuild the calipers, which is on the to do list, install speed bleeders which is tantalizing, and so on but, everything I have done to this point has not corrected it, and have done the major items.

 

I have no leaks, system has been flushed many times, fluid is recent.

 

I know these bikes, even when new were a little spongy on the pedal as noted by test riders of old magazines I have, so I have factored that in.

 

How can this system pull air into it, without having a leak, and has anyone really been successful on these VR's in having substantial rear braking that can lock the rear tire, as the couple that I have sat on seem to have the same issue.

 

Thanks

[Marcarl]

First of all, if you are getting air into the system, it' got to come from somewhere. Either the calipers, or the master. Most likely the master, for as the piston moves back it either sucks the fluid back, that should be under pressure form the calipers or it will suck air into itself if there is not enough pressure from the calipers. Bleeding does not seem to be a problem if I read your post correctly, you are getting a firm pedal and that means, no air, and no air is no air. Check out your master, by pushing it in and then slowly, very slowly releasing it. If you do this a number of times and get some air it would indicate a problem in fluid return, which could come from a stuck caliper, or it may be the rubber lines losing their elasticity. Also check out the rubber line from the reservoir to the master, make sure the clamps are tight, don't just feel them, actually tighten them.

If you at can see your way to do it, get steel flex brakes lines, I did and what a diifference. I'l never go back to rubber.

[Guest Bigin]

Thanks, have tightened the line between the master and the resorvoir, and the master is newly rebuilt.

 

So if my calipers are sticking, which I believe they are because they temporarily froze while the wheels were off. Had to use some Brakleen to get them moving for reassembly and had to remove them again due dragging on the rotors, it could cause reverse pressure drawing air into the system?

 

Where would it come in from?

[GeorgeS]

Simple due to AGE, 19 pushing 20 years !! rebuild the Calipers.

 

I know its a messy job, but I did them on my 89 3 years ago.

Believe me, they needed the rebuild. And, they were working OK

when I pulled them apart.

 

Get new kits, do the job, your life depends on it.

[Guest Bigin]

I agree, its in the works, not too bad of a job imho, just cant see how it could cause whats happening, but I am not the smartest guy in the world, thanks

[Squidley]

Just to play devil advocate, you did bleed the up on the dash area where the triple trees are correct. There is a bleed screw there that goes down to the left front caliper and can be overlooked.

Other than that everything else has been mentioned that I can think of right now

[Guest Bigin]

Yeah got that Squid. Its called the metering valve and is to be bled last. Its the easiest one! Thanks though.

[Rocket]

Played with this long enough, need new ideas.

 

 

Everything has been rebuilt with exception of calipers, but still has original lines.

 

 

I know I could replace the lines, not cheap, rebuild the calipers, which is on the to do list, install speed bleeders which is tantalizing, and so on but, everything I have done to this point has not corrected it, and have done the major items.

 

 

Thanks

 

For bleeding the masters, did you do these seperately, after the re-builds & prior to hooking up to the normal brake system??? AKA Bench bleeding in Automotive terms.........

 

I am not sure if it would make a difference in your case. Due to amount of fluid pumped through the system, but it may help determining the cause, of the problem....

[Marcarl]

Sorry I'm so long getting back to you, had some work to do on Scamper tonite.

If the calipers are slow to return, the master is not, so a vaccum is created in the system and the easiest place to get air is past the seals in the master. From what you lastly posted, I would take off the calipers, give them a good going over with new kits and clean up the cylinder with a hone, there must be no pit marks or scratches in the cylinder. Put it all back together and you should be home free. Everything needs to be clean, clean, clean.

Brakes are nothing to fool with, with out them working perfectly you'll be riding a wild ass torpedo.

[BradT]

Just a dumb thought, maybe your not getting it all out. When you pump the brakes you stir up the air.

 

Maybe if you bleed one valve let it sit, then do another and let it sit again.

 

Just another idea.

 

Brad

[Guest Bigin]

Thanks for all the input folks. Nice to be able to bounce a frustrating problem off someone with experience with these machines.

 

Still waiting for the seal kits to arrive.

 

Becoming obsessed with this bike I think.

 

Couldnt leave it alone so went out and bleed another half can of fluid through it.

 

Such an optimist.

 

Got it a little firmer, but the bubbles never stopped coming.

 

Im starting to believe some of the air seen in the bleed hose is coming from around bleeder when loosened slightly too much, and that its difficult to tell the air bubbles in the line from the bubbles that are pulled in from edges of the hose with the vacuum bleeder.

 

Can shut the bleeder valve and still have similar looking bubbles. May not be so much air in the lines as first thought. Vacuum bleeder may be adding to the variables here.

 

Would get very small and almost foamy if aggressively and quickly pumped the pedal in short strokes.

 

This also firmed the pedal more than using the long stroke to the bottom while bleeding.

 

Noticed a slight kink in the line between reservoir and master, new hose but may be a skosh too long. Is that a special type of hose? Problem? Beyond me.

 

Enough tonite, have an excuse for a test ride tomorow now, hehe.

 

Again, thanks all.