Quick rear brake help needed


11 replies to this topic
  • Moscow Roost

Posted December 04, 2011 - 04:45 PM

#1

Got an 09 YZ450F. Wanted to go to stainless brake lines. Front replacement went fine.

Rear is NOT working. Everything is tight, but when I compress the pedal and the MC cap is off, I get a bubble of air coming out the top of the MC??? Been trying to bleed the rear brakes all day to no avail. No pressure at the brake pads whatsoever. Can anyone help?

I've read some posts about removing the caliper and suspending it higher than the MC to make bleeding easier. Perhaps that's the ticket?

Switched back to the original brake line thinking the new one might have issues...same deal.

Brakes were working just fine before I started dinking with things. I know...I know...don't screw with things if they aren't broken. 41 and still learning lessons over and over and over again.

  • Kaw_04_250f

Posted December 04, 2011 - 06:13 PM

#2

Check out a YouTube video named "bleeding brakes part 1". Good luck, I've got 10 years on you and still enrolled in school of hard knocks. My wife tells me all the time .... The enemy of good is better!!

  • Moscow Roost

Posted December 04, 2011 - 07:31 PM

#3

Check out a YouTube video named "bleeding brakes part 1". Good luck, I've got 10 years on you and still enrolled in school of hard knocks. My wife tells me all the time .... The enemy of good is better!!

Thanks Kaw 04 250f. Funny...my wife tells me that "my saving money sure gets expensive"! I'll check out the video. Just tried another hour at it (beforehand) with no luck. Oh well... I only use my rear brake on special occasions.

  • Moscow Roost

Posted December 05, 2011 - 04:31 PM

#4

Bad news. Reverse bled the rear brakes and still have no pressure to the caliper. Still getting funny air bubbles coming up from the master cylinder when I depress the pedal. Weird that it would happen at the same time that I replaced the rear brake line. I'm not sure where to start...master cylinder rebuild or the caliper. Any help would be much appreciated.

  • grayracer513

Posted December 05, 2011 - 05:38 PM

#5

Fill the master cylinder reservoir full and stand ready to keep it full if it should drop quickly. Loosen the banjo bolt at the master cylinder/hose connection, push the lever down and close the bolt back up. Let the lever return to the top, fill it if need be, and repeat until mostly brake fluid comes out at that point. Then, open the rear bleeder screw and see if the fluid level will start to drop. If it does, you have a gravity bleed going. Keep the MC full and let fluid run through until it clears up. Tighten the bleeder. Tap the brake pedal a time or two to dislodge any bubbles under the fill port, and see what it feels like.

  • Moscow Roost

Posted December 05, 2011 - 08:38 PM

#6

I was hoping you would chime in grayracer.

I tried something similar to what you are describing yesterday but failed to close the banjo bolt before letting the pedal return to the top. After I reverse bled the brake today I got no air coming out of the Zerk when trying to bleed it, but never could build any pressure. The pedal goes all the way down with no resistance. Not sure what the air bubbles coming up in the master cylinder mean when I depress the pedal.

I am busy till Thursday, but will try your suggestion to the tee then and post the results. Regardless, I really appreciate your effort to help me out.

Edited by Moscow Roost, December 06, 2011 - 12:34 PM.
grammar


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  • Moscow Roost

Posted December 08, 2011 - 06:24 PM

#7

Fill the master cylinder reservoir full and stand ready to keep it full if it should drop quickly. Loosen the banjo bolt at the master cylinder/hose connection, push the lever down and close the bolt back up. Let the lever return to the top, fill it if need be, and repeat until mostly brake fluid comes out at that point. Then, open the rear bleeder screw and see if the fluid level will start to drop. If it does, you have a gravity bleed going. Keep the MC full and let fluid run through until it clears up. Tighten the bleeder. Tap the brake pedal a time or two to dislodge any bubbles under the fill port, and see what it feels like.

YES!!!!!!!!!!!

You are the MAN Grayracer! It worked and I couldn't be more pleased. Thank you so much for helping a fellow rider out. If you are ever in Northern Idaho, give me a shout. I owe you a 6 pack and some great single track.

  • grayracer513

Posted December 08, 2011 - 08:18 PM

#8

I owe you a 6 pack and some great single track.

Both good things. :lol:

The banjo fitting at the rear master is a high spot in the line, and the ring part of the fitting has enough volume in it to let a huge bubble park there. Fluid flowing through the system in either direction during bleeding just flows under the bubble without moving it, and unless you let it out first, you'll never accomplish anything.

  • MaxPower

Posted December 13, 2011 - 08:51 AM

#9

when changing brakes on my wifes car my neighbor let me use a brake bleeder. I heard of them but never really gave them a thought.

Now I have a new favorite tool. It took a long time to knock a Milwaukee Saw Zall off the top.

This brake bleeder kicked butt!!
It was one that you hook to an airline but they make hand powered ones.
I could replace all the old fluid in the lines in just a few minutes

I think it would be great to have one for the bikes. Rear brake fluid gets nasty from getting hot and nothing is better than a perfectly working front brake


  • grayracer513

Posted December 13, 2011 - 10:12 AM

#10

Simply changing fluid is easy, as does not require bleeding the brakes at all if you do it by just letting the old fluid drain while you simultaneously add new to replace it with.

But you're right. Power bleeder are the real deal.

  • revyrider

Posted March 22, 2013 - 04:54 PM

#11

Grayracer saved me hours of frustration with his post here on bleeding the banjo bolt on the rear caliper. After trying to bleed the usual way still had nothing! This tip WORKS!!

  • YZPaGuy

Posted March 22, 2013 - 06:58 PM

#12

No doubt it works. I wish I would have seen this earlier this week. I had the same problem. Somehow I mamaged to figure it out on my own but if I would have read this it would have saved me an hour minimum!





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