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gravityfreak

Spongy Front Brake

21 posts in this topic

G'day. I am new to the site so hello to you all !

I have a question about my '00 WR400. the front brake is quite spongy and I am overall quite unimpressed with the power. The bike may be an '00 model but it is almost new (long story). I am pretty good at bleeding brakes and am 99% sure there is no air in the system. I have flushed it with new fluid so it's not that either. Any ideas?

It doesn't pump up or fade - just has a spongy feel and a lack of power.

Thanks !

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I will be a good start to replace the "packings" in the mastercylinder, the smalle seals that is on the plunger, this have workede every time for me remember to lubricate.

And now that you have rippede the brakesystem apart I would also lubricate the pistons in the caliper, using brake lube

:thumbsup:

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gday, ive got the same problem with my 99 wrf, so replacing the seals should be the go? what about the brake line? are braided lines THAT much better?

cheers - Brett :devil::thumbsup:

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I have the same problem on my '00. You can squeeze the lever right to the bar. It didn't used to be this mushy. I bled it (correctly) so there is no air in the system, but to no avail. How does vacuum bleeding work? I'm going to get some new pads on it, even though the current set have plenty of life left. Maybe that will help a little.

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You most likely have air in the brakes. Take a tie wrap and tie the brake lever against the grip and leave it over night.

Next morning you should have no air.

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How does vacuum bleeding work?

it sucks the fluid/air out of the bleed nipple. You need the apropriate tool. Sometimes you get air trapped near the banjo bolt on the master cyl. After you've bled your brakes hold a little bit of pressure on the lever and crack the banjo bolt, but nip iut up again before the lever hits the bar. If this doesnt work you can remove the caliper and let it hang down on the floor overnight. Then place a bit of ply (same thickness as disc) between the pads and bleed the brakes again. Refit the caliper. If you still have a problem it's time for a mater cyl kit.

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Thanks Hamish and Beezer,

So when I tie off the brake lever to the grip and leave it overnight, I have to bleed it again right? I mean the air can't just disappear can it? I've got it zip tied all the way in to the grip right now so hopefully it will work out. :thumbsup:

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I have the same problem on my '00. You can squeeze the lever right to the bar. It didn't used to be this mushy. I bled it (correctly) so there is no air in the system, but to no avail. How does vacuum bleeding work? I'm going to get some new pads on it, even though the current set have plenty of life left. Maybe that will help a little.

Watch the caliper/rotor as you squeeze the lever, if you see the rotor flexing as you squeeze, the rotor is prob'ly warped/bent. I had the same problem, it was a severely bent rotor(my fault, forgot the disc lock was on...). Had the same prob on my 90YZ-WR, it was warping due to heat, I coned 2 rotors before putting an XT350 rotor on, per a Yam. Wrench Report.

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Thanks Hamish and Beezer,

So when I tie off the brake lever to the grip and leave it overnight, I have to bleed it again right? I mean the air can't just disappear can it? I've got it zip tied all the way in to the grip right now so hopefully it will work out. :thumbsup:

All you're doing is forcing the air into solution with the fluid, try bleeding it with the caliper hanging...

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Thanks Rich. It seemed weird though that there isn't any pulsing at the lever. I need to take a class on brakes I guess.

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Yep...when I coned the YZ-WR rotor it never pulsed....but you could see it flexing when you squeezed the lever.

The bent one pulsed real bad.....

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You are not forcing air in to the system. Using the zip tie method gets it out. I have a vaccum bleeder and on certain bikes you still will have air in the line. Zip tie the lever and leave it. The air bubbles will rise to the top of the line. When you cut the zip tie and the lever goes back into position the air is forced in to the M/C. You end up with a hard lever.

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Not what I said, Beez.....I said "it's forcing any air left in the system into SOLUTION with the brake fluid!"

Learn to read..... :thumbsup:

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Whatever it did, it worked! It's much better, but does anyone know if this is a temporary fix or will I be set for a while? Should I bleed it again?

Thanks again Beezer and Rich- :thumbsup:

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Well, I solved the problem. No bent rotor, vacuum bleeding or hanging calipers were necessary. I did bleed it again and that maybe helped a little. In the end it was new pads that firmed it up. Apparently the fresh pads push the piston back into the caliper enough to really tighten up feel at the lever. Thanks for the advice, though!

:thumbsup:

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