Front brake loses pressure

viking174
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viking174 3/9/2022 10:37pm
3/9/2022 10:37pm
Buy a new 2022 , problem gone. You’re welcome 😉
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mikeglg
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mikeglg 3/26/2022 11:53am
3/26/2022 11:53am Edited Date/Time 3/26/2022 12:18pm
A little update. Yesterday i bled the brakes using the pump and crack method and also tried something else. I pushed the caliper in order to fully compress the pistons and push the air, if there was any, up in the master cylinder. So i noticed some bubbles coming up and then the lever felt harder to pull. So i continued until the bubbles stopped. Then i pushed the caliper again and after some pumps, bubbles came up. It seems that every time i push the calipers, air is sucked from somewhere. I also tried reverse bleeding by pushing fresh fluid from a syringe up in the master cylinder. No bubbles came up with this method. This explains what i exprerience while riding. One moment the brake is good , then it sucks air and loses power, then after some pumps the air goes up in the master cylinder and brake power returns to normal. and it goes on.
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lostboy819 3/26/2022 12:17pm
3/26/2022 12:17pm Edited Date/Time 3/26/2022 2:45pm
If you have bubbles then you have air in the line. Now you need to decide if its sucking air into the system by a small leak or if it was just trapped air. Bottom line is if you are getting bubbles then there is air in the line. You have already said you have had leaks at the banjo bolts so you need to check everything. No leaks and then no air. If you cant figure it out then take it to someone who can because leaks can be hard to find and wont go away.
Sandusky26
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Sandusky26 3/26/2022 2:38pm
3/26/2022 2:38pm
I replaced my line and diaphragm and now my front brake works perfect, wanted to let you guys know.
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mikeglg
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mikeglg 3/27/2022 1:39am
3/27/2022 1:39am
Is it possible to suck air from the caliper pistons,maybe worn seals?Or it would cause additional symptoms too?
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RG38
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RG38 3/27/2022 3:41am
3/27/2022 3:41am
Had something similar on a YZ450. New fuild, pads and bleeding didn't make much difference. Mechanic felt the stock line may have swelled a little and we swapped for a braided GYTR line. Better than new after that.
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mikeglg
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mikeglg 3/27/2022 12:30pm
3/27/2022 12:30pm
update no2. I pulled the caliper of the wheel and i found out that the pistons dont move evenly. The upper piston moves half the distance of the lower piston , with each pump of the brake. Also the front wheel doesnt move freely, it has some drag. I swapped my front wheel with my buddy's yz250f and my wheel did drag on his bike too! So i think that because the pistons dont move evenly, the pads are worn out unevenly, causing the wheel to stick. So , does this explain what i exprerience while riding? For sure the brake doesnt work at his full potential.


It is obvious that one piston is working more than the other..

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mikeglg
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mikeglg 4/16/2022 8:30am
4/16/2022 8:30am
Bad news guys. I put a new braided brake line and a front caliper rebuild kit, and the problem isnt solved. Only happens in big braking bumps or braking after a big landing. In the road i can go 5th gear pinned and hit the brakes, and it works perfect. Something is wrong with the caliper. It seems that when the front end takes a beating the caliper moves and pads open. Also the front wheel has a lot of drag.
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Sandusky26
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Sandusky26 4/16/2022 9:29am
4/16/2022 9:29am
mikeglg wrote:
Bad news guys. I put a new braided brake line and a front caliper rebuild kit, and the problem isnt solved. Only happens in big braking...
Bad news guys. I put a new braided brake line and a front caliper rebuild kit, and the problem isnt solved. Only happens in big braking bumps or braking after a big landing. In the road i can go 5th gear pinned and hit the brakes, and it works perfect. Something is wrong with the caliper. It seems that when the front end takes a beating the caliper moves and pads open. Also the front wheel has a lot of drag.
I think my diaphragm had a hole in it and that was my problem, I always had fluid between the diaphragm and MC cap whenever I removed the cap. You could try that.
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mikeglg
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mikeglg 4/17/2022 11:03am
4/17/2022 11:03am
mikeglg wrote:
Bad news guys. I put a new braided brake line and a front caliper rebuild kit, and the problem isnt solved. Only happens in big braking...
Bad news guys. I put a new braided brake line and a front caliper rebuild kit, and the problem isnt solved. Only happens in big braking bumps or braking after a big landing. In the road i can go 5th gear pinned and hit the brakes, and it works perfect. Something is wrong with the caliper. It seems that when the front end takes a beating the caliper moves and pads open. Also the front wheel has a lot of drag.
Sandusky26 wrote:
I think my diaphragm had a hole in it and that was my problem, I always had fluid between the diaphragm and MC cap whenever I...
I think my diaphragm had a hole in it and that was my problem, I always had fluid between the diaphragm and MC cap whenever I removed the cap. You could try that.
No, i have never noticed fluid in the diaphragm.
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