Redback Motorcycle Smash Repairs - 1/ 9 Collie St, Fyshwick. Ph: 6280 5433

Rear Brake Issues

Discussion in 'Tech Help' started by Chalky, Dec 8, 2015.

  1. Chalky
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    Chalky Member

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    I took my rear brake lever off and once putting it back on it doesnt work well at all.

    It feels like the brake lever travels until it hits the end of its travel then hits a wall.

    I tried draining the brake fluid and even turned the rear caliper upside down (as recommended) to get all the air out of the system, however i cant seem to get pressure into it from using the brake pedal at all.

    Is there an easy way to check if my Rear brake master cylinder is busted? Or anything else i should look at?
     
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  2. Ron50
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    Ron50 Member

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    Make sure there's enough travel in the lever to uncover the return hole so the fluid can get back from the pressurised side of the master cylinder piston to the reservoir.
     
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  3. gazman
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    gazman Member

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    it's either not put on the spline in the same position or there is still air in the calliper or line.
    The rear takes ages (30/40 minutes) to bleed if it's been emptied as it only pumps a tiny bit at a time until nearly all of the air is out.
    Turn the calliper upside down sitting on the disc (or just jam something between the pads) so the the nipple is facing up and tap on the brake calliper and brake line as you pump . That will help dislodge the bubbles faster.

    To bleed the rear it helps to run clear hose/tube off the nipple straight like a meter or more high before falling into your catch can , you can see the very fine bubbles are pushed through. Also once the fluid is up the tube a bit e.g 150mm air can't get back in the calliper through the nipple.

    Bunnings has the clear tube 5mm I think in the sprinkler section.
     
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  4. Chalky
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    Chalky Member

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    Yeah i might take the rear wheel off and really spend some time on it.

    Theres plenty of travel for the lever, it just feels like the master cylinder has been pushed in and its stuck in or something. Theres no pressure what so ever for the whole lever travel until it pushes fully into the master cylinder and cant move any further. No movement in the pads what so ever.

    It started happening after i removed the brake lever and had to re-insert the cylinder push rod, i only fully drained it afterwards to try and rectify it.
     
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  5. gazman
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    gazman Member

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    sounds like air in the system . Stick with it, without pressure the rear master cylinder will only pump a few ml's at time.
     
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  6. Ron50
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    Ron50 Member

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    If there's no fluid in the master cylinder to compress you might need to use a pump on the bleed nipple to get the piston back and fill the master cylinder.
     
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  7. Ron50
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    Ron50 Member

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    Fluid can't get through from the reservoir until the piston moves back far enough to uncover the hole I referred to earlier.
     
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  8. Chalky
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    Chalky Member

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    Ive been using a mightyvac to suck the fluid through, and i dont think theres a bleed valve on the rear master cylinder?

    Ive definitely been able to suck fluid through the reservoir though from the bleed nipple on the caliper.
     
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  9. Chalky
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    Chalky Member

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    Thanks guys for the help, i will let you know how i go
     
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  10. Ron50
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    Ron50 Member

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    I meant pump the fluid through from the caliper bleed nipple to push the master cylinder piston back. Sounds like when you were making clearance for the rod to go in you pushed the piston in too far - further than it would go in normal operation. You'll probably need to rebleed the system again when everything's back in place.
     
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  11. Chalky
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    Chalky Member

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    Yeah that sounds about right.

    I might have to google how to push fluid back through it, or maybe my mightyvac can push also... hmmm worth a try.
     
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  12. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    A syringe will push fluid through from the caliper up to the reservoir.
     
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  13. Chalky
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    Chalky Member

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    Had a set of new tyres fitted today and they said they would check out my brake. They didnt flush it or anything and Im not sure what they did, but it works again now. hahaha.
     
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  14. G-relk
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    G-relk Moderator Staff Member Moderator

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    They'll have pushed the pads all the way into the caliper to get the wheel back on without too much fucking around. This would have burped some air out of somewhere, which has obviously been your problem.
     
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  15. Chalky
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    Chalky Member

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    Hmmmm, single sided swingarm means they dont have to touch the rear brake caliper to remove the rear wheel. I also tried that when i was doing a proper upside down flush. Might have to just ask them. haha
     
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  16. Yedi
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    ?

    Still need to slip the disc back between the pads... Hence the pushing of the pads back into the caliper that was mentioned above :D
     
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  17. G-relk
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    G-relk Moderator Staff Member Moderator

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    Ha, forgot about that. I have NFI then.

    Not on a single swinger you don't. Rear wheels on single sided swing arms are mounted like a car wheels. That's why they were developed in the first place, to make rear tyre changes easier for race bikes.
     
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  18. Yedi
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    Oh... Did not realise that! Learn something new every day :D:up
     
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  19. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Yep, the disc stays firmly attached to the axle on a Ducati.

    [​IMG]
     
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  20. Chalky
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    Chalky Member

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    Im heading back in on saturday to pick up the old tyre (wrong sized one from the Bday ride) so if i get an explanation from them i will post it here to let you guys know :)
     
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