Caliper pistons not moving evenly

austin.wampler
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austin.wampler
Edited Date/Time 1/18/2013 2:26pm
2009 KX450F

Just added an oversized rotor kit and SS brakelines. Bled the brakes and have a great lever feel but only the top piston moves. The bottom piston will move very slowly if the top piston is engaged but the difference is drastic. The brakes are wearing uneven.....

How do i fix this? Please help. I've spent so much already to rectify this.

No leaks in caliper or master cylinder.
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DTHA70
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DTHA70 1/17/2013 3:08pm
1/17/2013 3:08pm
either the pistons are sticking or, most likely, the caliper guide pins are sticking.
austin.wampler
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austin.wampler 1/17/2013 3:14pm
1/17/2013 3:14pm
Its the piston. I am able to watch the top piston move outward while the lower piston stays idle until the top piston has nowhere to go.
scooter5002
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scooter5002 1/17/2013 3:54pm
1/17/2013 3:54pm
Quite possibly the bottom piston is slightly seized. Don't forget, fluid takes the path of least resistance. With the caliper off the bike, put something between the top piston (keep it close to bottomed) to stop it from moving, and see how much lever effort is required to move the bottom. Don't let it shoot out of the bore of the caliper, you'll probably need something to block it in. You may need to remove it and clean the bore or piston.
austin.wampler
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austin.wampler 1/17/2013 5:41pm
1/17/2013 5:41pm
@scooter

Thank you, I have a set of seals (top &bottom) on the way. I will be taking the caliper apart ASAP>

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lumpy790
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lumpy790 1/17/2013 7:52pm
1/17/2013 7:52pm
clean the groove the seals go into really well..... I use a tiny welders wire brush
MOTODAD422
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MOTODAD422 1/18/2013 2:26pm
1/18/2013 2:26pm
And remember to only use brake fluid to lubricate the seals upon assembly.

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