rear brake caliper problem



3 replies to this topic
  • will1894

Posted January 04, 2016 - 04:39 PM

#1

Today I put new brake lines and pads on my 2008 yz450f the front went fine and I thought the rear was going good got everything on and bleed my lines but the rear caliper piston won't come back out after I compressed it to put the new pads in Iv bleed the line about a dozen times now and nothing the piston will move a little when I press the brake peddle and move back but I can't get it to come out to make contact with the pads any help would be very appreciated 



  • fulton246

Posted January 05, 2016 - 08:03 AM

#2

Might be time for a caliper rebuild. I had the same thing happen to me on my RMZ. Ended up replacing the pistons and o-rings and it is as good as new. The piston and o-ring kit cost about $35, but I threw in stainless lines and fast/quick bleeders so all total it cost around $100. 

 

P.S. The easiest way to get the pistons out is to remove the caliper from the bike and spray 125 psi of compressed air into the port where the brake line goes. Just be sure to have the pistons pointed away from you (preferable aimed at the floor or into a pillow) because they will come shooting out like a rocket. 



Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted January 05, 2016 - 08:58 AM

#3

 

P.S. The easiest way to get the pistons out is to remove the caliper from the bike and spray 125 psi of compressed air into the port where the brake line goes. Just be sure to have the pistons pointed away from you (preferable aimed at the floor or into a pillow) because they will come shooting out like a rocket. 

 

Dangerous advice and unnecessary.

 

The hydraulic system the caliper is connected to is easily capable of raising more pressure than needed to push the caliper piston back out, and even if you get it back out, you'll have the same problem, which simply is that the system still has so much air in it that it's inoperative.

 

Start by filling the master.  Open the bleeder, press the pedal down semi-gently against its limit, hold, and close the bleeder.  Return the pedal and repeat this until it appears that there is no air in the fluid being exhausted from the bleeder.  During this process, it is important to keep the fluid level up in the master. 

 

Next, it's time to get rid of the giant bubble that lives at the banjo fitting where the brake line ties to the master cylinder.  Loosen the fitting, push down and hold the pedal, retighten the fitting.  You'll see air.  Repeat until you don't (usually 1-3 times).  The system should now be functionally free of air and capable of pushing the pads back out.  It may take several strokes of the pedal to run them back down, and you'll want to keep an eye on the level in the master.  At the end of the task, you want the level about three quarters up in the sight window, but not higher.



  • will1894

Posted January 05, 2016 - 10:31 AM

#4

Thanks y'all I don't think there is any air in the line but ill try messing with the banjo fitting and see if that works first, i was thinking of using a air compressor to get it out but i want to use that as a last resort but ya its probably time for a rebuild







Related Content

Reviews

Yamaha YZ450F 2017 by Chris.GVS


Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017
Wiki
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info


Articles
  • 0 replies
Forums
Photo

Should I buy this bike? help....... by Numsa Hul


Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies
Forums
Photo

YZ450FX OR YZ450F by MESSMAKER


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  30 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.