KDXRIDER.NET

99 KX125 forks

RB Axle kit

Wheel spins free without caliper mounted but seems like pads won't let go of the rotor once caliper is on.

It looks like the rotor is centered in the caliper just fine but spin the wheel and there is definite rubing going on.

Idears?

Are the slides free? Is the caliper piston sticking? Is the master cylinder hanging up? Is the brake line pinched off somehow? ?

LOL.... not quite the "Oh just do this" answer I was hoping for but, all stuff I will check out.

Thanks for the thourough reply

I had to do some grinding on my caliper mounts to make mine fit

at these two spots I ground the shoulders off so they are flush

Something else to check:

In the master cylinder there is a little hole that lets the pressure off when you release the lever. It can get plugged up with deposits from old fluid (happened to me on two bikes I bought used). Take a wire out of a wire brush and make sure it is clear. On the KDX, it is under the rubber "plug" in the master cylinder.

One more thing, I replaced the stock front brake lever with a aftermarket lever and it fit fine and worked fine. Until I rode the bike a very short distance and the front wheel started to drag very bad. The new lever would not let the plunger in the master cylinder return all the way and was holding the brake partially on and with a little heat it really got tight.

Did you by chance replace the front brake lever?

I used a set of 00 KX 250 forks with the RB axle and the KDX brake. Everything went right on fine with no issues. I have a few hundred miles on them and they seem to be fine with no funky wear or other issues.

Thanks for all the feedback guys.

I'm wondering of it's Rbates or GSA's idea about the caliper not returning to the correct position. It's still the same brake lever as before but that was good thinking.

Wibby, I saw how you had to grind on your caliper. Was it obvious that you needed to? Mine looks like it's mounting up and aligned perfect. I wonder if I'm missing something.

I think I'll try and clean that caliper tonight.

To clean it, do you just pull the pads, pump the caliper all the way out, wipe the piston down, push it back all the way in, remove and dirt and then mount it back up?

BTW....don't want to spill any beans but. The little I have ridden on these new forks........I am in love. I should have done this three years ago!

If the caliper is sticking it will be hard to push back in. You should be able to stick a screw driver between the out side of the outer pad and the caliper and pry it back easily. If you can not push the piston back than loosen the bleeder and try it again. If it goes back with the bleeder open then the problem is in the master cylinder.

I think the grinding that wibbens did was to center the rotor in the caliper and not so much to remove a drag.

When you put the caliper on does the mount touch the fork or do you have to draw it up tight to the fork leg with the bolts?

Also if you pop the piston out you should replace the seals in it before reassembly.

I would clean and grease the pins that the caliper floats on before taking the piston out of the caliper. That way you make sure the caliper self-aligns.

I was racing My KDX this summer in a HS. The front brake started to drag a little, and then got hot and wouldn't release pressure. The problem was in the master cylinder. I opened the bleed screw, and it released enough pressure to let me get back to the pits. Taped a wrench to the crossbar pad, and continued in the race and tried not to use the front brake.

I account it to one or all of 3 things, in order of likelihood:
1) the relief hole in the master cylinder was plugged up
2) I had just adjusted the lever and got it too tight (like rbates said)
3) the brake pads were very thin, and let lots of heat into the caliper

I backed the lever off at the pits but the problem did not go away for the rest of the race. I rebuilt the master cylinder and replaced the pads, and the problem did go away.

Back to the beginning, are you using the KDX brake setup that was working fine on your bike or are you using the KX brake set up that you have not seen work?

mine was definitely dragging, could not even spin the front wheel

Yes, using the original KDX brake setup.

If you compress the piston and put the caliper back on will the wheel spin? Dose it only drag after you have pumped up the brake? On mine when I am putting the front wheel back on by the time I get everything lined up just the wiggling of the wheel will push the piston back in enough so it takes pumping the brake a few times before there is any type of firm lever.