spongy front brake


8 replies to this topic
  • paulson

Posted January 07, 2007 - 05:12 PM

#1

It all started when I blew a front fork seal but kept riding for the day. The brake quit working but I figured it was just the fork oil. I came home and bleed them and put new pads on and cleaned the disk really good but they are still really spongy. When I bleed them I tapped the line and put a pint through. Could there still be air (I dought) or did something go wrong inside.
I dont know why anything would go wrong in the caliper from oil being on the disk but I dont think there would still be any air in the line either cause there was barely any when I bleed them out.
06 yz450 w/ only about 50 hrs on it.

  • christoswr

Posted January 07, 2007 - 06:15 PM

#2

Bleeding the brakes can be a really easy thing or a pain in the ....
I'm not an expert but i would say there is still some air trapped in there.
I've done this several times in my bike in just 5 minutes but last time i did it it took me 30 minutes!!
Good luck and be patient!

  • Baron Von Beard

Posted January 07, 2007 - 06:19 PM

#3

It can be tough to get the air out. Fill the MC and pump it to make sure the pads are against the rotor. Pull the lever in and hold, crack the bleeder, close the bleeder and then, this is important, let the brake lever snap back. Don't simply release the lever, let it snap back as quickly as possible. Pump the lever back up and repeat until it feels like it's as good as it'll get, paying attention to MC level. After that, pull the caliper off the rotor and compress the piston in as far as possible to back bleed the system. This will push any air back up the line and out the MC. Be careful though because if the MC is full when you do this, fluid may over flow out the MC.

  • flintlock28

Posted January 07, 2007 - 07:15 PM

#4

Beard, what is the rationale for letting the lever "snap" back??
I've never heard this one before...

When I bled my front brake, I became infuriated because I got the brake 95% bled, but it still had a slight sponginess to it. Even after reading ton's of post's, I still couldn't get it 100%. Turns out someone mentioned the back bleed tip, and that did the trick.

I'll reitierate.....Make Sure you push the Caliper piston all the way in, or you'll never get that little bit of trapped air out.

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  • Baron Von Beard

Posted January 07, 2007 - 09:15 PM

#5

One guy gave me the tip when I was working on a Harley once. He didn't give a real reason for it other than it worked. After a whole day of trying to bleed the front brakes on my bike, I tried the snapping trick and they were bled in 5 minutes. Your guess is as good as mine, all I know is it's worked on every bike I've ever worked on.

  • KJ790

Posted January 07, 2007 - 09:15 PM

#6

It's supposed to help make any bubbles come out better. I have also heard of factory mechanics putting a zipty around the lever and the throttle to hold the front brake on and leaving it over night.

  • Baron Von Beard

Posted January 07, 2007 - 09:17 PM

#7

It's supposed to help make any bubbles come out better. I have also heard of factory mechanics putting a zipty around the lever and the throttle to hold the front brake on and leaving it over night.


I've heard that as well.

  • torqueme

Posted January 08, 2007 - 12:01 AM

#8

Mity-Vac is a wonderful thing. just attach the vacum hose to the bleeder on the caliper-fill the MC-crack the bleeder & vacume the fluid through the line. close the bleeder-refill MC-pump lever 3 times & done. got mine from MAC tools & use it on everything from my bikes to clogged sinks.

  • Fastest1

Posted January 08, 2007 - 04:35 AM

#9

Back bleeding is a good technique, you can use the pump technique as mentioned above but leave the caliper bleed screw open after the 1st pump and watch the fluid level in the master closely. Dont let it get low and close the bleeder after a bit of fluid has drained through. Gravity works well also.





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