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Back Brake Problems> '04 450

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Hey guys, I have lost my back brakes... there is no pressure in the system at all, I can push the pedal all the way down with my fingers... There is No leaks in the system though... I have bled the brakes, put in a master cylinder rebuild kit, and a new brake line.... And it still wont gain any pressure. Anyone else have this problem?! What did you do to fix it!?!? 🙂

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I'm guessing you've got a sticky air bubble in the MC. Crack the banjo at the MC just enough to leak, wrap a towel around it to keep the fluid off sensitive parts, and bleed the MC. Once the MC is pumping you can finish bleeding from the caliper banjo.

Mity Vacs also help to pull recaltrant air out of MCs and union junctions. Usually you have to undo the caliper bleed nipple completely and use one of the Mity Vac suction cones to avoid the vacuum leaking across the bleeder threads.

Keep at it, there ain't much there to can cause problems.

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I know, thats why Im so confused. I don't get it. Even if I put new fluid in it, how can there still be a bubble...? The line is completely free of fluid, then once I put new stuff in, and bleed it til there's no bubbles it still has no pressure. But I went and bought brand new Dot 4 fluid... trying that today, and bleeding the hell out of the system. Hopefully it works, its been nice here for like 3 weeks and all I've rode is 4 motos. Im T.O.'d.

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The line is completely free of fluid, then once I put new stuff in, and bleed it til there's no bubbles it still has no pressure.

I thought this was only an issue on '02s, this hasn't happened to my '03, but anyway I've seen exactly what you describe due to damage to the MC plunger.

On a riding buddy's '02 it seems that, during one of those team GPs, the brakes were fading and the riders kept putting more pressure and exerting more travel on the MC. This damaged the MC plunger and the brakes quit working altogether. I looked at it for him, and somebody here posted the same issue, so we replaced the plunger and fixed the problem.

But, like I said, I haven't heard about this lately on the newer Hondas.

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By the plunger you mean...? The rod that comes out of the MC and attaches to the Pedal? New brake fluid worked good on the front, nice feel to the lever... but still no pressure on the back... we're trying a vaccuum. If not, I will try the rod. Or a new bike lol

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Get one of those nifty kd air operated bleeders. Bleed the poop out of it then also tap on the lines with a screwdrive going to the master cyclnder with the cap off. IF this does not work bleed at line fittings.

Flyn Ryan

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I just bled and bled and bled and bled and bled and bled and bled and bled and bled. And it worked... so far.lol

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Yah, I replaced that, it comes in a kit, the master cylinder rebuild kit. With the two seals, the actual piston, and the spring.

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I had the same problem on my 03 too.

I swear I bleed that dam line for hours on end and it finally came back. It turned out to be a 2 man job.....that extra hand helped!!

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I just bled and bled and bled and bled and bled and bled and bled and bled and bled. And it worked... so far.lol

Honda brakes are by far the hardest to bleed IMO. I had trouble with my rear brake too, one thing I noticed helped in the process, was usig a syringe and pushing fluid through the caliper while moving the brake pedal up and down.

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