Front brake locking up!

[dustinklassen]

Hey guys I just bought an 08 yz250f last Saturday and raced it Sunday. Both motos I had to stop racing because my front brake was locking my front wheel solid! I didn't get hurt so that was good.

Now I need help fixing this. I don't know what's wrong. Brakes are good for 2-3 laps then the lever progressively gets harder and harder to pull eventually it's rock solid and the brakes are on 110%

I tried bleeding them

Flushing out the system

I cleaned out the calliper but couldn't get the system bled after that.

Anyone else ran Into the brake lock problem?

[WALKINGWOUNDED]

Are the caliper slide pins clean and greased?

 

If you remove your brake pads, the caliper should slide side to side easily on the pins if they are clean and greased.

 

Also make sure your brake lever isn't adjusted too tight against the piston in the master cylinder.

[gimped up]

This^^^^

Couldn't get better advice.

[WALKINGWOUNDED]

A quick test to find out if the problem is hydraulic of mechanical, is to ride the bike until you feel the brake beginning to drag.  Put the bike on the stand, and make sure the wheel is still stuck/dragging. 

 

Then open the bleeder on the caliper.  I brake fluid spurts out, and the wheel frees up, then its a hydraulic problem.  If you open the bleeder on the caliper and no fluid spurts out, and the wheel stays sticking/stuck, then the problem is mechanical at the caliper/wheel.

Edited August 3, 2014 by WALKINGWOUNDED

[WALKINGWOUNDED]

P.S. While you're riding the bike trying to get the front brakes to lock up, avoid 105ft step-ups, and 93ft doubles.  Just sayin 

[Wait a while]

P.S. While you're riding the bike trying to get the front brakes to lock up, avoid 105ft step-ups, and 93ft doubles.  Just sayin 

Yeah and make sure it isn't your hand still clamped around the lever. Cos that would be my problem if I was doing that stuff. 

[717 MOTORSPORTS]

Your master cylinder needs to be rebuilt. Kits are available, they're cheap, and it's easy to do.

[dustinklassen]

Thanks guys I'll do some more testing today. I'm bringing it to a mechanic regardless but if I could get a ride in today yet that would be sweet haha. 

 

And Walkingwounded that is some good advise haha, I was lucky at the races that it didn't lock up over the step up. I caught it the second time in a corner just before a set of rollers so that was nice I didn't have to experience locked brakes through them. 

[WALKINGWOUNDED]

Thanks guys I'll do some more testing today. I'm bringing it to a mechanic regardless but if I could get a ride in today yet that would be sweet haha. 

 

And Walkingwounded that is some good advise haha, I was lucky at the races that it didn't lock up over the step up. I caught it the second time in a corner just before a set of rollers so that was nice I didn't have to experience locked brakes through them. 

 

 

On a somewhat related subject, if your ever in the air and front end is high and can't tap the rear brake, quickly pop the front brake and it will tilt the bike down like the rear.  It's an odd feeling though, the back of the bike comes up and if you're standing the seat will hit you in the hiney.  Just make sure your bars are not turned.

[schrode]

i've had this problem on my husky where basically the brake drags progressively and does the same thing as yours. mine was a lever adjustment issue. it was engaging the MC piston a little too much causing drag, fluid kept heating up and expanding applying more and more pressure to the pads.  simple lever adjustment and they work great now.

[dustinklassen]

On a somewhat related subject, if your ever in the air and front end is high and can't tap the rear brake, quickly pop the front brake and it will tilt the bike down like the rear. It's an odd feeling though, the back of the bike comes up and if you're standing the seat will hit you in the hiney. Just make sure your bars are not turned.

I will remember that haha. I'm still getting used to movement in the air so I'll try practicing that.