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help with rear brake problem

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2005 CRF450x, stock brake system. My rear brake stopped working. I can push the pedal all the way and barely get any braking. When this first happened I noticed the reservoir was low but no apparent leaks anywhere. So I added brake fluid and bled the system and the brakes worked.. rode for about 5 minutes and back to no brakes. Master cylinder rebuild? Caliper?

Thanks!

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2005 CRF450x, stock brake system. My rear brake stopped working. I can push the pedal all the way and barely get any braking. When this first happened I noticed the reservoir was low but no apparent leaks anywhere. So I added brake fluid and bled the system and the brakes worked.. rode for about 5 minutes and back to no brakes. Master cylinder rebuild? Caliper?

Thanks!

Try adding more fluid and re-bleeding.

If you let the reservoir get too low for too long, the master cylinder piston will corrode, and you need to rebuild/replace.

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I got snakebit on this once. Everything was working in the garage and on the stand. But when I rode the bike, no brakes. Turns out it was an anuerism in the brakeline, in the sharp bend behind the master, where you could not see it, while the bike was fully assembled. I only found it after I pulled the rear wheel and the caliper. I was then able to twist the brake line around to inspect it all the way around, under pressure, and viola' ! The most minute bubble you can imagine, but it did not leak. It just expanded under pressure, severely reducing the pressure to the caliper. I replaced the brake line and end of ordeal. :thumbsup:

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I got snakebit on this once. Everything was working in the garage and on the stand. But when I rode the bike, no brakes. Turns out it was an anuerism in the brakeline, in the sharp bend behind the master, where you could not see it, while the bike was fully assembled. I only found it after I pulled the rear wheel and the caliper. I was then able to twist the brake line around to inspect it all the way around, under pressure, and viola' ! The most minute bubble you can imagine, but it did not leak. It just expanded under pressure, severely reducing the pressure to the caliper. I replaced the brake line and end of ordeal. :thumbsup:

Thats a new one. Good catch.

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I didn't notice any leakn but it was low so musta gone somewhere. Thx everyone, I'm gonna check the line and rebleed again

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I know that this is a "rear brake" problem, but just food for thought. When you replace the brake pads keep in mind that you need to "break" or "wear" them in. Usually, about 4-5 hard stops from 20mph before they will become effective.

Also, keep any chain lube or wax over spray away from the disc, this will render them useless, instantaneously.

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I didn't notice any leakn but it was low so musta gone somewhere. Thx everyone, I'm gonna check the line and rebleed again

Have you considered that when the pads wear down more fluid is sent down the lines to the caliper as the piston pushes out?

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