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Discussion Starter #1 (Edited)
TL;DR: In spite of changing the brake lines, bleeding the brakes to a firm lever, and using the zip-tie trick; the front brakes keep losing a firm lever. They need to be pumped to regain pressure. I did the same on the rear brake, and it works fine (even the ABS). Is my caliper broken?

Details:
2017 FZ09 ABS. Over a week ago, I forgot to take the disc lock off my front right disc. I didn't drop the bike, but afterwards I noticed that I lost pressure on the front brakes. They need to be pumped to regain pressure. It would disappear quickly. I got home, only using the rear brake. I decided to replace all my brake lines with spiegler lines, change pads, and rebleed. (my previous brake fluid was two years old)

After hours, I replaced the lines and pads front and rear. I bled the brakes, getting to a firm lever front and back. On the front brakes, I bled the left caliper, then the right, then the left, and then the right. The front brake however wouldn't keep the firm lever after a few minutes. I bled the brakes a bunch of times. No help. (The rear brake had a firm pedal.) I ended up leaving the pedal depressed (with a wedge), and the lever squeezed for five days.

I went out for a ride today. The rear brake works fine, I even tested the ABS. The front lever keeps repeatedly losing the firm lever. I don't see brake fluid leaking out of anything. Pumping temporarily returns pressure.

Question:
What should I check? (Should I just go to the shop?)

thanks,
Paul
 

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Did you follow the directions for bleeding the ABS? Most ABS systems require a special procedure or a vacuum bleeder to do the job properly.
 

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If this started happening right after the disc-lock incident, and before you even started to change out the lines, I would definitely suspect something happened to the caliper. There must be some air getting into the system, or the caliper itself could be broken. If you can't diagnose the issue with 100% certainty, take it to a shop. Brakes are absolutely critical to your safety, and you should not ride the bike until it's fixed.
 

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I suspect a warped disc or mounting. As the wheel spins it's pushing the pistons back into the caliper and that's why the lever travel increases when you ride it, you're having to pump the pistons out before you can get pressure.
Get the front wheel off the ground, spin it by hand and brace a screwdriver or similar on the fork just a couple of mm's away from the disc friction surface. It's crude, but it'll show any runout. Or get a workshop to check it with a dial gauge.
And, all disc lock users have done this, welcome to the club.
 

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Discussion Starter #6
I suspect a warped disc or mounting. As the wheel spins it's pushing the pistons back into the caliper and that's why the lever travel increases when you ride it, you're having to pump the pistons out before you can get pressure.
Get the front wheel off the ground, spin it by hand and brace a screwdriver or similar on the fork just a couple of mm's away from the disc friction surface. It's crude, but it'll show any runout. Or get a workshop to check it with a dial gauge.
And, all disc lock users have done this, welcome to the club.
I agree with the warped or damaged disc rotor theory especially in light of the disc lock incident.
The warped/bent disc idea is the most compelling. I'll be persuing this idea.

Unfortunately, I have to wait for a part for my stand. I'll follow up with the thread once I can check this out!

Thanks everyone

Paul
 

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Agree with LouG.
Warp disc will push the brake pads away, the reason why you need to pump the brake lever to bring it back to the rotors. I'm sure the bleeding part you did is just fine. On some race track we used what we called "knock off springs" behind the caliper pistons to fix this issue with vibration at very high speed. In your case the rotor is warp I bet.
 

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Discussion Starter #9
I took a straight edge down to the garage and applied it to both rotors. The one I thought I had damaged, allowed me to rock the straight edge on its surface. The other side did not.

Based on this, I think the rotor is bent, and I ordered an oem replacement.

I don't have a tool to measure run-out, but I may try with calipers after the disc is off the wheel.

Thanks again for the guidance folks!
 

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Definitely sounds like a bent rotor if you can rock a straight edge on it! 😳

I still can't figure out how a simple disc-lock jam - which many of us have done at some point - could actually bend a rotor, but that should fix it. Let us know how it goes when you get the new one on...
 

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I've heard of all sorts of damage. If the lock hits the caliper or fork at an angle it could put side force on the disc. I hope the carrier is still true.
 

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Discussion Starter #12
I think it could be because my disc lock looks like a mini u lock. It may have twisted the rotor when the lock hit the caliper.

Sent from my SM-T510 using Tapatalk
 

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Suggest if you want to continue using the disc lock form of bike security attached a bright colored chord or string to the lock long enough to hook onto your throttle grip as a reminder the lock is on before your try to throttle away from a parking spot.
 

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Discussion Starter #14
I just thought of adding a key blank to the reminder cord so I cannot enter start the bike while forgetting.
 

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I've had disc locks for about 4 years, but have only used them a few times. But when I do, I try to run the front tire up to a curb or something that will require me to back up, so I don't try to ride off with the disk lock attached. I realize that's not always practical though.
 
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