WR450 rear brakes don't work....HELP!!!!

:):) I got caught up in some barbed wire around my rear brake line and caliper. I replaced rear brake line, piston and dust seals, and a bent pad clip. I bled the system and nothing. There is no change in the feel of the brake pedal. It feels like there is no resistence at all, the caliper piston doesn't even look like it wants to move. My next step is to tear apart the master cylinder and check the O rings. Beyond that, I'm lost. Maybe replace the piston? The bike is a month old, it's driving me nuts looking at it and not being able to ride it! PLEASE HELP!

Did you lose all your fluid? You may have air trapped in the system. Have you cracked the bleed screw and stepped on the pedal? Does fluid come out when you press? I wouldn't think you have component failure-Air can be a tricky thing :)

I bet you just have lots of bleeding left to do. I have changed the fluid on my old WR426 on the front and rear and bleeding all the air out is slow. Just keep on bleeding, it will soon get back the feel. Just give it time. The teeny little master cylinders doesnt displace too much volume compares to an auto.

You need a vacuum bleeder to do a good job and take the unit off the rear swing arm and make sure the air moves up to the bleed screw. Bleed the master as well. Even fully bled the system is slightly mushy on the rear brakes. :)

I bled the system 4-5 times over the past 8 hrs. There are no more bubbles. The piston isn't moving at all. Even if there is a small amount of air in the system, wouldn't the piston move a little? I rode 3-4 times after I removed the barbed wire and the brakes worked fine. Then on my last ride they just stopped working all together. What else could it be if bleeding the system is not working? O rings in the master cylinder? Gremlins? I'm lost! :)

You got! :p The master seals are shot if you cant get pressure after all that bleeding. :) I still think you should try a vacuum bleeder. The rear brakes on these bikes are a biatch to bleed! :)

Another option:Open the top of the master cylinder,get a syringe, fill it with brake fluid, attach a hose between the fluid and the rear caliper bleed nut, open the nut and reverse the flow of brake fluid, add fluid until the bubbles stop.

You shouldn't need to pump the pedal but any movement will dislodge air bubbles..

Watch the mess as the master cylinder over flows.

This has always been a quicker, better way for me to bleed systems.

You need a vacuum bleeder to do a good job and take the unit off the rear swing arm and make sure the air moves up to the bleed screw. Bleed the master as well. Even fully bled the system is slightly mushy on the rear brakes. :)

I was having difficulty bleeding the rear brakes on my WR after replacing the brake switch on the master cylinder. What I did was remove the caliper from the swing arm and zip tie it up with the muffler. I then went through the normal bleeding process and was finally able to get the trapped air out of it.

thanks for the suggestions. I will try some more and let you know how it turned out.

Another option:Open the top of the master cylinder,get a syringe, fill it with brake fluid, attach a hose between the fluid and the rear caliper bleed nut, open the nut and reverse the flow of brake fluid, add fluid until the bubbles stop...

This was the only way I could get the pedal to "firm up" & start actuating the caliper when I swapped out my rear line. :)

I tried your suggestion to fill a syringe and "back bleed" the system andI finally got some movement. I can still move the rear wheel if I try. I have'nt ridden on it yet, but i doubt they would skid if applied fully. It seems the brakes work better if i pump the pedal a few times. What can I do to make them better beyond trying to bleed more? Thanks for the help. :)

You may have to take the caliper off it's mount & hold it below the S/A with the banjo fitting being the upward most part of the caliper while doing the "reverse injection" method. This should ensure that all the air leaves the cavity of the caliper. I also did a few runs of "normal" bleeding (pump up the M/C, crack bleed screw & press lever) after the reverse injection, just to make sure no air bubbles came out.

You cant beat a $15.00 vacuum bleeder kit from Auto parts store! You will never ever bleed brakes without it again! The flow just moves pesky little air bubbles out of the system. :)

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