125-200cc WR 125 - Problems with the brakes..

I own a 06'-07' WR 125 bought new before half a year and lately I was having problems with the front brakes. The master cylinder was losing pressure every time I was braking steadely and the braking was really poor.

Firstly I changed brake fluids with no difference. Then I bought a brembo rebuild kit that costed more than 60euros. The old parts were like new when I disassembled the master cylinder but after fitting the new kit the pressure loss was fixed. However, the lever is still very spoongy and the feeling is poor.

Any idea what else to look for ? Maybe disassemble the caliper too ??

bleed it.

What Sceep said. Buy a cheap brake bleeding kit off the internet, bleed and enjoy sponge-free brakes!

I did that several times with the traditional way but didnt see any improvement.. Maybe I ll try again and again .. :P

There is a brembo trick to drill out the banjo bolt at 90 degrees to get better bleeding. I usually just swap to a Honda CRF master.

To me sounds like the master cylinder may be bypassing fluid (pushing fluid back past the main seal back into the reservoir). The easiest way to check this normally is to clamp the brake line and pull the lever in. If the lever slowly comes back to the handlebar you have a problem. But considering you may have a braided line clamping it is not the best option. I would recommend pulling the caliper off push both caliper pistons back in and clamp the pads hard up against the caliper body. Then try and see what happens with the lever. Also by pushing the pistons right back in may also push back any air trapped high in the brakeline/master cylinder. Now if bypassing is your problem there is only a few things you can do.

Strip the cylinder and check it for any pitting in the cylinder bore( this is created by moisture accumulating in the fluid ) If pitted either buy a new cylinder or find someone that can re sleeve it and fit a new piston and seal kit. Be mindful that Dot 3/4 brake fluid is Hygroscopic and absorbs moisture from the atmosphere. Brake fluid should be changed every 12 months in my books. The wetter the conditions you ride or live in the sooner it should be replaced.

The possibility of the line being bad, had the same problem on a 2000 WR 360 rear brake. Replaced the line and now it acts like it should.

Needs bled properly... Sometimes a bit of air can get trapped in the master cylinder... It is not a simple straight-forward job if you havent done it before. For the amount of money you've dropped in the rebuild kit, and if your not getting results by doing it yourself, take it in to have it done.

Brilliant piece of troubleshooting !!!

Hello again. Thanks for your advice guys!

Well, the pressure problem seems to have been fixed after I fitted the rebuild kit. The main problem now is that the brakes come a bit late at the lever movement. In fact the bike starts to brake after I have pushed the lever half way in. The brakes are good after that but this doesn't help to have a good feeling. Note that I have set the lever adjustment full screwed in (lever at higher position).

What can cause this problem? Probably air in the brake line? Next week I ll try to empty the whole system from fluids, check the caliper's pistons movement and refill it again.

no need to completely drain it, as you will be starting over... Grab a cheap vacuum bleeder and keep running oil through it. I tip the bike, tap on master cylinder, and on the lower unit to try to dislodge any air bubbles... Then keep bleeding.