yz 250 front brake rebuild/maintenance?

[mike-evans]

I have a 01 YZ 250 2t with a poor front brake. I put new pads on it and bled the front brake, it is spongey and give it a hard pul and it wil come into the bars, also the front wheel is not completely free spinning, it rubs on the pads as if they are not completely returning...should i rebuild the mc and or caliper or wil i be wasting my money, could the caliper just need maintenance i.e clean the pistons and surounding area? Does anyone know how to do work on the caliper? How do i establish poor seals in the system?

 

[Matt90GT]

you need to grease up the slide pins on the brake caliper also. Ie remove the pads and pull the caliper off the mounting bracket.

also check that the disc is not bent or warped. Those were solid disc from the factory.

If you really want a good brake, get a late model CR/CRF master cylinder and brake line and do a direct route brake line like the CRF and late model YZs have.

 

[GoldDrum]

If the break lever is spongey and hits the bar then it sounds like they are not bled completely. I put a new calipur on my son's kx65 and it took a long time to get it bled completely. It was spongey and then got firm finally.

 

[mike-evans]

If the break lever is spongey and hits the bar then it sounds like they are not bled completely. I put a new calipur on my son's kx65 and it took a long time to get it bled completely. It was spongey and then got firm finally.

what did you do to sort it? I have bled and bled them and no joy, quite possibly air in system...i have heard people removin the system from the bike and hanging it up to do it, so the air rises out of the system? I need to strip the caliper and grease up the pins etc as they dont completely return and cause the disc to rub when rotating...anyone stripped thier calipers, wouldnt mind some advice on doing that, never done it...

 

[GoldDrum]

I have never torn one from a bike down and greased it. I had a new one I was putting on. It did not look like it was that much to it as far as greasing and making sure that it moves freely. Someone else here may have a better idea. I know I just kept filling the resivoir and bleeding until it came up. I almost gave up a few times thinking I was getting nowhere. It took a long time.

 

[Brandon H.]

I had no problem bleeding my brakes, maybe I got lucky? Def grease the pins, I have rebuilt 4 bikes so far, all of them had really dry crusty pins that needed grease. Taking the brake system off and holding it up a little might help the air get pushed out like you said, just make sure fluid always stays in the line. Keep those pins greased, and put anti-sieze on the bolts for the pads.

 

[mike-evans]

A guy I spoke to said he fits a syringe ful of fluid to the caliper bleed nipple and pushes the fluid up through the caliper through the pipe and out of the mc to remove all the air bubbles...anyone done it this way?

 

[mike-evans]

UPDATE..I disassembled the mc and caliper inspected seals and pistons, and all seems fine, refitted everything and attempted to bleed it. Started by doing it the normal way, by filling mc up, pumping leve, close lever, open bleed nipple (clear tubing attached and into a bottle of fluid), closed nipple and released lever. As i close the bleed nipple release the lever i can see the fluid in the clear tubing moving back up towards the caliper?? I then tried, filling mc up,connecting a syringe onto the bleed nipple and drawing out the syringe which draws fluid and lots of bubbles out?? I then tried connecting a syringe ful of fluid to the bleed nipple and pushing the fluid up through the system...all the procedures i used all resulted in the same affect, lever feels hard but give it a good squeeze and you can get it into the bar?? Am i doing something wrong? ps the fluid in the mc never dropped enough to suck air in ;)

 

[julien_d]

I've spent hours bleeding before. It's a real bear to get all the air out of there. You can bleed from the banjo bolt at the MC line if necessary. Sometimes air gets trapped there and it can be almost impossible to force it all the way down and out the bleeder.

 

[mike-evans]

I've spent hours bleeding before. It's a real bear to get all the air out of there. You can bleed from the banjo bolt at the MC line if necessary. Sometimes air gets trapped there and it can be almost impossible to force it all the way down and out the bleeder.

What procedure did you use to bleed the front brake? When I atached an empty syringe to the bleed nipple, i would open the nipple (doing this with the mc ful of fluid), draw out the syringe and it would draw out a little fluid, then bubbles would come out, then more fluid..i done that for about 20 mins and it didnt seem to get any better.....also, when i fitted the mc cap and rubber seal back on, when i squeeze the brake i could see a bubble of fluid come out through the little cut out on the seal and mc cap..is this normal?

 

[Matt90GT]

you have a 9 year old bike. the brake lines wear out and start ballooning. Time for a new front brake line!

This is what you want:

http://www.lightspeedperf.com/produ...413&prevaction=category&previd=17&prevstart=0