Front Brak Problem (wierd)

[BlackWombat]

I have a wr450 that i ride on the street mostly and the front brake sucks. Like the preasure behind the leaver is weak and stopping power is weak but as i was riding it today all the sudden the the brakes felts great. The leaver had lots of preassure and there was good feel. the braking power still lacked a bit but i think it needs new brake p[ads any way. I have Bled the system multiple times with a vaccum to fix it but i have no clue why this would happen or why the preassure is so low in the first place. Some one have an idea why the preasure is so low and why it would feel good all the sudden and then go back to crappy?

[Stealth13]

Would there happen to have been air bubbles in the line? That can make it how you described

[zibbit u2]

75% of the time, the fix for issues like your describing is bleeding the system, the other 25% of the time is hardware related... i.e... brake line stretch (from rubber hose), or possibly a master cylinder that's in need of a rebuild which is allowing the brake fluid to bypass the piston, thereby reducing the efficiency of each lever pull or stroke.

[FORMA MOTO]

Clean the pads and disc, replace the line with a braided one, rebuild the cylinder, and force-bleed the system from the bottom up, with the pistons fully compressed.

[1987CR250R]

It's hard to say what weird is because The Brak Show is about one of the weirdest I have seen.

And for those that haven't figured it out yet, many front brake lines are braided (starting in 86/87). The difference between OEM and the expensive aftermarket? A clear jacket to showcase the stainless braid...

A lot of things cause weak or spongy brakes. The Yamahas have a downward loop in the front brake that makes it exceptionally difficult to bleed but if you can figure out how to do it there really isn't much of a difference in performance vs other manufacturers. Also kow that many manufacturers have different compounds and performance is greatly affected. I will never run another EBC product on any of my bikes after running a set of their ceramic pads folllowed by a set of their metallic pads.

Edited March 29, 2012 by 1987CR250R

[MANIAC998]

You might need a front master cylinder rebuild. Like RS25 said, you might be getting leakage past the piston in the master cylinder, which then isn't sending full pressure to the caliper. Maniac