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Front Brake Soft

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This really isn't model specific.   My son dumped his bike at the track the other day and it wouldn't start.  So I was bump started it and noticed that his front brake was super soft, pulled all the way in to the grip and wouldn't stop the bike.  Then I pulled it a few times and it felt fine again.   So I kept pulling it and noticed that after several pulls it would go soft and then all of the sudden back to normal.

I opened the bleeder and pumped through new oil and it felt good and then all of the sudden back to being soft.  

Any ideas ?

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that is what I did.  It must have a leak but no fluid is leaking out so I am think perhaps air is getting in.   Did a good search and found I may have to get a master cylinder kit.

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There has to be air getting in somehow. It doesn't just go soft like that. I'd check all your fittings and stuff, make sure they're nice and tight. Also look for any spots on your brake hoses that may be leaking in air. Could be the caliper leaking somehow too.

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Soft brakes can be dangerous man. I'd get that fixed as soon as possible. I've had some avoidable incidents occur had I fixed soft brakes on my bikes.

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Did you back bleed from the bottom up, i.e. pumping brake fluid through the brake 'bleeder valve' into the brake MC reservoir with a syringe?  Note that it is difficult to properly bleed brakes by attempting to bleed by pumping brake fluid through the so-called bleeder valve since air bubbles naturally rise to the top.

 

Two time honored methods for the 'spongy brake syndrome', both with the brake MC cylinder as high as possible:  1) Bungie the brake lever in towards the handlebar and let sit overnight.  This oftentimes allows trapped air bubbles to escape into the MC reservoir.  2) Push the brake pucks in which forces air bubbles up into the MC reservoir.  You can do this by gently prying the brake pads apart with a large screwdriver then pumping the brake lever several times until the brakes are back.  This may need to repeated once or twice.

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I will be looking at this again tonight.   The boy said it started after he fell and his bike went down on that side so its possible that there is damage to brake lever, maybe a torn rubber letting air in.

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Drained oil again and pumped in from bleeder valve.    Still goes soft.    Will have to pull brake lever off and dismantle to see if I can figure out where its leaking

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