2012 KX250F Front Brake Mushy and barely works

neverstop
Edited Date/Time 8/9/2015 11:51am
Hello

I took my forks off to get them revalved, friend pulls brake when I'm about to put forks back on with no tire on so its locked shut. I pry them open and get tire back on, two rides later my front brake is mushy "have to four finger pull the brake lever to stop, even then it's scary/dangerous" before this problem it was rock solid one finger half pull for a full stop not sure if it's a coincidence or not. I'm stumped as to why my front brake is so mushy still. It has been looked at by multiple people and a mechanic multiple times. No air in line, smoothed out the pistons in caliper, new brake pads, tried different lever for shits and giggles, seals are all fine in caliper, line seems fine, brake rotor isn't warped, tire is aligned properly. Any ideas? I'm thinking it's the master cylinder, but how would that be caused from prying open the caliper?

Cheers!
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mxtech1
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mxtech1 7/30/2015 7:25am
7/30/2015 7:25am
You need to completely flush the system with new fluids. I would recommend investing in a hand-vacuum pump to pull the fluid through. This really is the surest way to bleed brakes.

You can also scuff the glaze off the rotor and pads with red scotch-brite. This may restore some performance.

If the fluid change fails, you probably need to rebuild the caliper and master.

Prying open the caliper did not cause any of your issues. It's coincidental.
neverstop 7/30/2015 9:22am
7/30/2015 9:22am Edited Date/Time 7/30/2015 9:23am
100% no air in lines because mechanic used a vacuum bleeder. And I personally did bleeding with a pump, everything from banjo bolts loosening, reverse bleeding etc. Weirdest problem I've had with brakes, it won't build pressure no matter what, I'll rebuild master cylinder and see.
Paw Paw 271
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Paw Paw 271 7/30/2015 10:20am
7/30/2015 10:20am
If there is too much fluid in the master it will not allow the master to work correctly.

Paw Paw
MX690
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MX690 7/30/2015 3:14pm
7/30/2015 3:14pm
Pump your brake lever a few times then zip tie it to your handlebars and leave it over night. Works perfect on my sons KTM.

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neverstop 7/30/2015 5:55pm
7/30/2015 5:55pm
MX690 wrote:
Pump your brake lever a few times then zip tie it to your handlebars and leave it over night. Works perfect on my sons KTM.
Tried this and your right it usually does work but did 0 difference this time, and fluid level is fine pew pew not too much.
mnomis484
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mnomis484 8/3/2015 2:50am
8/3/2015 2:50am
Forks leaking oil on the brake disc?
Aceofspades 8/3/2015 2:12pm
8/3/2015 2:12pm
Never underestimate a full disassemble/cleaning. My 2000 kx250 had shit brakes and a disassemble/cleaning and new fluid made them one finger stoppers; and even new those model kx had shit brakes. I think especially if the piston comes out too much and is pushed back in that dirt ends up getting in the seals. After assembly and bleeding, pull in the lever and zip tie it to the grip. Next morning youll have STRONG brakes.
Calhoun117
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Calhoun117 8/9/2015 11:51am
8/9/2015 11:51am
So I'm having a bit of problems with my front brakes to and this is my question..I've heard of the zip tie your lever in over night routine multiple times, what does this accomplish? I know it makes the brakes harder in the morning and what not, but what's the theory behind why this works? To me it just seems dangerous to have that much pressure applied for so long, but I have no idea, just wondering why it works and what it actually accomplishes to get the result of better "harder" brake pull

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