KDXRIDER.NET

Hi Guys,

I hope someone can help me out. I have changed my forks to kx125 yr 2000 and need help to sort the front brakes out.

I have re-used the braided line from my original forks but no matter what I try I cannot get the front brake to feel firm.

Before I swapped the brake lines over the kx125 set up was razor sharp and firm, swapped over I cannot get anywhere close.

I have tried the traditional method but after a considerable time (and fluid!) I have not achieved much. A quick search on here sugggested I use the pressure method, I have done that with some improvement but it still feels spongy! What am I doing wrong, this is driving me nuts!

thanks in advance
Gert

Unless you are using the same master cylinder and caliper, I would bet that the master cylinder needs to be rebuilt. There's a rebuild kit from the dealer and it's posted around here somewhere. Your old master cylinder is a direct replacement for the KX one but I'm not sure of the caliper.

Hi, thanks for the quick response.

I am using the complete kx front end with the single exception of the brake line, and thats a braided variety used on the original set up.

As the brake was firm before I changed over the lines I have put it down to my obviously lousy brake bleeding ability!

I seem to recall the original front brake on the bike when I bought it was adequate but not fantastic, I did not realise until I bought the complete kx front end and compared the feel of the brakes, the kx was super firm.

Is it really difficult to get these brakes bled well so there is no sponginess?

cheers

My trick is to push the brake fluid up from the bottom since air likes to go up anyway. I take a long piece of clear tubing, aquarium stuff will do, and then put it in my bottle of brake fluid and with my mouth I syphon it full. I put one end on the caliper bleed nipple and remove the master cylinder cap. I then crack the bleed nipple and put a velcro strap on the brake lever to open the master cylinder. I then blow air into the hose using my air compressor and back feed the caliper. I can watch the fluid in the clear hose and when it gets near the end, I quickly close the bleed nipple. It's messy at the master cylinder end of things, so do it over some rags.

You can now put the cap back on the MC and remove the velcro strap. Pump up the lever and it should be as firm as it's ever gonna get. If it's still mushy, it's rebuild time...

Hi Skipro, thanks for the detail, I will try the velcro trick as I have not done that before, should I pull the lever all the way in or part way to open the cylinder? cheers Gert

Just pull it all the way in. You need to open the passage for the fluid to get through the brake line. If the lever isn't pulled, it won't be possible to bleed.

I've done this same bleed method but in reverse;
Hook a long empty clear tube like aquarium tube, to the bleed screw, open the bleed screw and while standing up at the MS, start sucking on the tube and pouring brake fluid into the master cylinder. It's potentially not as effective since bubbles naturally want to go up, but it will work. In the first method, you will SEE the micro bubbles as they are pushed up and into the MS. One way to keep that method neat is to enlist a buddy to siphon the MS before it overflows. A hypodermic or turkey baster will work.

Thanks for the detail, much appreciated!
Gert