2000 yz250 front brake - won't hold pressure

[breakdirt916]

took a tip coasting down a hill and bopped the master cylinder...since then, when you grab the front brake, there is no pressure.

If you pump the lever a few times, it will build pressure and hold it, but if you let the lever go about halfway, all the pressure is released.

I unbolted both of the banjo bolts, emptied/cleaned the master cylinder, used a vacuum pump to pull fresh fluid through the system, but it's still the same...

google doesn't match my specific scenario, so the only thing I can guess is a seal with the plunger in the master cylinder popped when I fell...I either need to rebuild it, or start replacing pieces (brake lines and/or calipers) until it sorts out

anyone experience this or have an idea of how I can fix my current system?

[dougie]

Rotor straight? If it got dinged it will push the pads apart as it rotates and you will need to double pump the lever to feel anything

[Rambunctous]

One time I had a similar issue. I put on a new master cylinder after a crash. Would not pump up correctly. Fiddled & diddled. Finally I removed the lever and used a rod and pushed in the piston a few times and held it in and let the air out. I repeated a couple times and I replaced the lever and was good to go.

[Pigman]

I have a master off a WR450 in mint shape for sale.......

[TheIglu]

You need to replace it with a radial master from a GSXR.

[breakdirt916]

Rotor straight? If it got dinged it will push the pads apart as it rotates and you will need to double pump the lever to feel anything

rotor straight...the double pump is required at a stop or move and independent of rotor position - but good to know!

One time I had a similar issue. I put on a new master cylinder after a crash. Would not pump up correctly. Fiddled & diddled. Finally I removed the lever and used a rod and pushed in the piston a few times and held it in and let the air out. I repeated a couple times and I replaced the lever and was good to go.

hmmm...I am also suspecting the master cylinder...but unfortunately I'd say mine was busted up when I tipped over. I've seen rebuild kits, but I'm not sure if I broke the mater itself, and not the parts that are replaced in a rebuild...

ordered another master cylinder...should be here Monday

I have a master off a WR450 in mint shape for sale.......

all good...found another one, thanks!

[breakdirt916]

was just the master...swapped it out and good to go!