Brake Caliper and Piston question

Discussion in 'The Club House' started by ShagNasty1001, May 31, 2013.

  1. ShagNasty1001

    ShagNasty1001 New Member

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    Alright y'all, got a small debacle and I can't seem to find much on it from google. The rear brake on my Yamaha is seized up. But not like it would be normally. The piston is stuck inside the caliper and won't budge at all. I've already flushed the system, checked the line for kinks to make sure it's getting fluid to it and everything. Even sprayed a de-greaser lubricant on it and re-lubed it but still nothing. Any ideas? I'd like to avoid taking it to a shop due to the outrageous hourly charges
     
  2. MOshooter

    MOshooter New Member

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    You will need a air compressor,take your caliper off the bike,drain the remaining fluid,now where the brake line attaches use a air nozzle with a rubber tip that will fit the brake line opening.
    Be very very careful not to get your fingers in the way of the piston that should shoot out like a missile,don't ask me how I know. :) lol

    Inspect your piston for pits or rust,if it's in bad shape you may need to order a new piston along with a seal kit.
     
    Last edited: Jun 1, 2013

  3. ShagNasty1001

    ShagNasty1001 New Member

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    Is there any way besides an Air Compressor? I don't have one where I live
     
  4. rockratt

    rockratt Active Member Lifetime Supporter

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    Air compressor is best but I have pulled them off and used the brake pedal but it makes a mess. Also when using an air compressor I lay a wooden hammer handle inside the caliper to catch the piston. And lastly I am not sure about how it is in the motorcycle world but in the automotive world you can buy a rebuilt caliper for just about the same price as you can build one anymore.
     
  5. kfox75

    kfox75 Well-Known Member Supporter

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    Diagosis of the problem would be easier with the year and model.

    Since you don't have a compressor, use the brake pedal to build up the pressure needed to pop the piston out of the bore. When you do this, take an old towel and fold it over then stick it between the piston and the caliper on the stationary side. This will catch the piston and reduce the amount of mess from the brake fluid when the piston come out. Or see if you have a friend that will let you use their compressor, and do the same thing with the air hose atachment.

    Contact your local Yamaha dealer, oe check the internet for a caliper rebuild kit for you bike. You will need sandpaper, a scotchbrite pad, brake cleaner, and some fine steel wood. With the piston out of the bore, inspect it for rust, pits, and cracks. Check the seals for tearing or cracking. Remove the seals and clean both the bore and the piston with the above mentioned abrasives , starting with the sandpaper, ending with the steel wool, using the brake cleaner between products, and rinse the bore and piston with the cleaner after you use the steel wool. Be gebtle. All you are trying to do is remove the rust and crud from the parts. Only use the Scotchbrite and steel wool to clean the grooves for the seals, and make sure the a completely clean before installing the new seal. Make sure you remove the banjo bolt (Hose xonector) and the blleder screw when you start the process, and leave them out until you have put the caliper back on your bike.

    To re-install the piston after the seals are replaced, line up the piston with the bore. Next, Put the stationary part of the C-clamp on the outside back of the bore, and the conpressing side centered in the piston, and start cranking. this should center and seat the piston in the bore. Re-install the caliper on the bike, hook up the brake hose, and bleed the brake. Your rear caliper is now rebuilt, and you should be good to go.

    rebuilding the caliper is about a half hour to 45 minute job. and the parts, assuming that you caliper and piston are in good shape,should e less than $30. Best of luck, and let us know how it works out
     
  6. ShagNasty1001

    ShagNasty1001 New Member

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    It's a 2012 Yamaha FZ6r. And I'll have them check it if I can't get it working when I take it up for an oil change next week
     
  7. kfox75

    kfox75 Well-Known Member Supporter

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    Another option occurs to me. If the caliper is still on the bike, apply the rear brake, and give the caliper a couple raps with a soft faced hammer. It may loosen up the piston. You may have to reset it with a C-clamp a couple of times and repeat the process, but this may work.
     
  8. ShagNasty1001

    ShagNasty1001 New Member

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    I actually never thought of that.. I have a rubber mallet at home, sitting on the dining room table
     
  9. therewolf

    therewolf New Member

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    Be very careful of the brake fluid.

    It is hydraulic fluid, and will instantly

    remove the paint from any surface

    it touches.
     
  10. danf_fl

    danf_fl Retired Supporter

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    Sometimes a little brake fluid applied around the outside of the cylinder may help (as well as other suggestions given.)
     
  11. MOshooter

    MOshooter New Member

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    kfox75 That's a very well written tare down and rebuild information,I should've gone further with my post,I missed writing about the emery cloth or sandpaper to clean the original piston if it was reusable....Nice post
     
    Last edited: Jun 3, 2013
  12. MOshooter

    MOshooter New Member

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    Good Advice therewolf,that brake fluid will bubble paint and some plastics right in front of your eyes that fast!
     
  13. kfox75

    kfox75 Well-Known Member Supporter

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    Thank you MO Shooter. My dad and I ran a small ATV, snow machine, and cycle repair business for about 15 years. I used to do about a cozen caliper rebuilds a month on average. Still doing it now from time to time, but most of those repairs are for family and friends. Been maducally retired for the last 7 years.
     
  14. ShagNasty1001

    ShagNasty1001 New Member

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    Just wanted to update y'all. I took the whole caliper off the bike and when I pressed on the read brake, there was hardly any fluid that came out. Is that normal? My mechanical skill set isn't the greatest and I haven't really done much before, except change the brake pads
     
  15. ShagNasty1001

    ShagNasty1001 New Member

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    Also, I got in contact with a local shop and they thought it could also be a master cylinder problem since there is no pressure or fluid being exhorted when the lever is pressed down
     
  16. kfox75

    kfox75 Well-Known Member Supporter

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    to answer both questions, yes. The flat side of the piston sits in the bore, so it doesn't take a lot of fluid to push it. The problem could also be in the master cylinder, but i would do the clean up and rebuild on the caliper first. After that is done, put it back on and see if the problem persists. If it does, replacing or R&Ring the mastercyender would be my next step. If the piston was going out and sticking there, I would suspect the brake hose. Since the piston was not moving there a three posibiitied as to what is causing it. They are:

    1. The caliper it's self.
    2. A loose fitting in the hose, line, a banjo bolt, or a loose bleeder screw. other than that, a cracked component such as the piston, caliper, or master cylinder. However, if the brake pedal was not moving, I would not suspect a leaky component.
    3. The master cylinder it's self may have an issue. In that case I would just order a new one, install it, bleed the system, and you should be good to go.

    Continue with the caliper, and see if it fixes the problem. If it doesn't, check your lins and hoses next, if there is no visible problem, remove and rebuild\replace the master cylinder.