2017 kx250f front breaks locked up

treylies
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Fargo, ND, USA

I have a 2017 kx250f with front break locking issues. I got to where I was planning on riding, I take the bike out and the front brakes slowly locked. Then sat on the side of the road for a little bit, they unlocked then started to ride back to the truck. They locked up again without touching the break, then they unlocked again after a little bit of sitting. What would be a quick fix I could do besides taking the brake off. because I wanted to do a hill climb even this week 

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walent215
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7/2/2024 11:54am

Remove some  of the fluid and check lever fitment 

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treylies
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7/2/2024 11:56am
walent215 wrote:

Remove some  of the fluid and check lever fitment 

Lever is good and I flushed the fluid 

7/2/2024 12:19pm

Still have to much fluid in there. Your brake rotor spining in between the pads still creata heat and causes the fluid to expand and locks your front brake up. Then as it cools the fluid contracts and frees the disk. Either that or your caliper is sticking. Moneys on the fluid. Seen many people do this over the years.

2
gscx
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7/2/2024 12:20pm

Did you just put on a new front brake lever? I have had one where it engaged the piston too much and when it heated up it would drag and lock up.

1

The Shop

treylies
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Fargo, ND, USA
7/2/2024 12:26pm
gscx wrote:
Did you just put on a new front brake lever? I have had one where it engaged the piston too much and when it heated up...

Did you just put on a new front brake lever? I have had one where it engaged the piston too much and when it heated up it would drag and lock up.

Haven’t messed with the lever but I just put new pads in 

treylies
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Fargo, ND, USA
7/2/2024 12:27pm
Still have to much fluid in there. Your brake rotor spining in between the pads still creata heat and causes the fluid to expand and locks...

Still have to much fluid in there. Your brake rotor spining in between the pads still creata heat and causes the fluid to expand and locks your front brake up. Then as it cools the fluid contracts and frees the disk. Either that or your caliper is sticking. Moneys on the fluid. Seen many people do this over the years.

So flush the fluid or what should I do? 

40acres
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Houston, TX, USA
7/2/2024 1:23pm
treylies wrote:

So flush the fluid or what should I do? 

You don't need to flush it, just remove a little bit. Your brake system is likely overfilled.

treylies
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Fargo, ND, USA
7/2/2024 1:27pm
treylies wrote:

So flush the fluid or what should I do? 

40acres wrote:

You don't need to flush it, just remove a little bit. Your brake system is likely overfilled.

Remove some from the line or the reservoir?

40acres
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7/2/2024 1:29pm
treylies wrote:

So flush the fluid or what should I do? 

40acres wrote:

You don't need to flush it, just remove a little bit. Your brake system is likely overfilled.

treylies wrote:

Remove some from the line or the reservoir?

Whatever floats your boat. Probably easier and less of a mess to pop the bleeder open on the caliper. 

joelsmith
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Marysville, OH, USA
7/2/2024 2:13pm Edited Date/Time 7/2/2024 2:14pm

Same thing happened to me years ago. The caliper seals were frayed and not allowing the pistons to retract. Grabbed the brake at the end of a 4th gear straight and became a lawn dart. Once I got home from the ER it had some drag but rolled. Rebuilding the caliper did it. Cheap and easy 

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lodewijk
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Djee, NL
7/2/2024 11:29pm
joelsmith wrote:
Same thing happened to me years ago. The caliper seals were frayed and not allowing the pistons to retract. Grabbed the brake at the end of...

Same thing happened to me years ago. The caliper seals were frayed and not allowing the pistons to retract. Grabbed the brake at the end of a 4th gear straight and became a lawn dart. Once I got home from the ER it had some drag but rolled. Rebuilding the caliper did it. Cheap and easy 

I'm not saying it didn't happen, but it sounds very unlikely that frayed seals can hold that kind of braking pressure to cause you to endo. Unless you mean they kept the pads in contact with the rotor constantly and thus overheating the system eventually. Still there should be enough air buffer in the reservoir to accommodate the expansion in that case.

As mentioned above, what OP has is likely overfilled reservoir or poorly adjusted lever that is keeping pressure. Most likely the former as he put in new pads

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