Rear brake issue 04 250X
  • harm5y
    Posts: 14
    Joined: Sun Aug 12, 2018 4:25 am

    Rear brake issue 04 250X

    by harm5y » Fri Nov 30, 2018 6:02 pm

    Peoples,

    Having some rear brake issues, after a big ride the pads were getting down and lost some feel so decided to replace the pads and fluid. Changed the pads out and the. Bleed the old fluid out until all the new had worked it’s way through. But I couldn’t get the pedal to firm up at all and the piston won’t move. I re-bleed again to make sure I hadn’t sucked air in by accident, I then bleed backwards using a syringe, still nothing. I’ve now pulled the whole unit off in one piece and bleed on the bench with the MC below the caliper to make sure any air goes up. Still getting no movement or pedel feel. I could hear what sounded like air passing through the MC when I was manually depressing, I also did notice an air bubble appear. I wondering if the main cause could be the MC not producing enough pressure and also sucking air in? Or is it the caliper? Should I look at replacing the line also?

    Cheers in advance for the help.

    Warren
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    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Rear brake issue 04 250X

    by JimDirt » Fri Nov 30, 2018 7:05 pm

    Are you using a vacuum bleeder ??? , its best to use one when bleeding these systems , it sounds like maybe there is air in behind the pistons in the caliper , you need to draw fluid thru it to push the air out

    Try this , take the caliper and squeeze the pistons all the way in (using a brake pad and something to pry it over) , then put both pads back in (with the system on the bike as it should be) and see if it starts getting pressure back when you start pumping the pedal , make sure the master does not get low on fluid as it does not hold much and its easy to suck air (keep the lid off till the system is fully bled), and make sure when releasing the bleed screw you are holding the pedal all the way down until the bleed screw is closed again so it is not allowing air to return into the system , ....... By pushing the pistons in , hopefully you will push the air out of it , then you should be able to bleed it back thru .....
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • harm5y
    Posts: 14
    Joined: Sun Aug 12, 2018 4:25 am

    Re: Rear brake issue 04 250X

    by harm5y » Sat Dec 01, 2018 1:56 am

    Used a one way valve type bleeder, don’t have a vaccum one (might go pick one up though. I’ve had the whole assembly out and hanging so hopefully any air is no longer caught anywhere. I’ll re install it and try your piston trick. Failing that im thinking either the MC air caliper May need a rebuild.
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Rear brake issue 04 250X

    by JimDirt » Sat Dec 01, 2018 10:17 am

    Yea these systems really need a vacuum bleeder to bleed correctly , just go to Harbor Freight and get one , they are about $25, it is what I use

    https://www.harborfreight.com/brake-ble ... 63391.html

    https://www.harborfreight.com/brake-ble ... 69328.html
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • harm5y
    Posts: 14
    Joined: Sun Aug 12, 2018 4:25 am

    Re: Rear brake issue 04 250X

    by harm5y » Sat Dec 01, 2018 1:00 pm

    Cheers for your help, I’ll get onto it!

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