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Discussion Starter #1
Hi guys

After an unfortunate trip into the bushes my front brakes are acting up, and I was hoping somebody could help me out figuring out what the problem is..

The symptoms: I have to squeeze the lever three times before the brakes start pulling. Squeezing a forth and fifth time feels and have the same effect as the third time (i.e. pulls the brakes). But if I e.g. roll the bike a couple of meters I'm back to start again and need to squeeze the lever three times to brake.

Background: Now, I have a feeling I'm not looking at just air in the system and the need to bleed. The brake fluid was changed two months ago, the reservoir was full, so I guess there's limited amount of air that could have gotten into the system (despite that the bike was laying "upside down" for 4-5 hours). The reservoir also has some visible scrapes, so there's a possibility other brake parts took a hit during the fall, but I don't know what would cause this behavior..

Bike: 2006 600rr - stock brake system

Please let me know your two cents before I start messing with the bike ("mess" - that's usually what happens when I start "fixing" stuff on my bike:)
 
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Warped rotors.

Put the bike on the front stand, pull the brake calipers off, and spin the tire with a dial indicator on the rotor.
 

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Discussion Starter #3
Wouldn't warped rotors cause pulsing braking and/or uneven drag when the bike is rolling? None of that is the case here. I don't have a front stand so I'm not able to check you suggestion right away..
 
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Slightly warped rotors would cause that, but warped rotors will push the pads apart which pushes the pistons back into the caliper. That requires you to pump the lever to get the pad back to the rotor, but since it's bent it'll keep being pushed back into the caliper.
 

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agree with demented there, same thing happened with a friend's GSXR1K when he hit someone in front of him. time for new disks.
 

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Discussion Starter #6
That actually makes sense! Although I don't have the front stand, a quick test shows I only need to roll the bike equal to about one wheel-length before I have to pump three times again. While wiggling back and forth on the same spot did not "reset" the brakes, which supports what you're suggesting!

So, the obvious followup-question, once I've properly verified that it is warped (and which one), do I have to change both or just the warped one? What about pads, would I have do change those too (they have 2,5k miles on them)
 
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Pads should be fine and you'll only have to replace the bent one, though I suspect both would be.
 

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Discussion Starter #8
Ok, I'll get hold of a front stand and check them properly. I'm hoping to get away with only changing one of them though, the rotors don't come cheap :/

Thanks for all the advice and info demented, I'll keep you / the thread posted along the way! :)
 

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Put the bike on its side stand and get a friend that you trust to pivot it up so that its resting on the rear wheel and the stand, then check the disk. Should only take around 10 seconds to do the full revolution and take your measurement.
 

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Discussion Starter #10
Verified today! The left front disc is bent. It's not visible just looking at the disc (e.g. from above), but is noticeable when I pivot and spin the front wheel. The right one looks fine from what I can tell.

I'll start looking for a left front disc brake with approx 2-3k miles. Let me know if somebody have any for sale; from what I've seen '03-'06 600rr and '04-'05 1000rr rotors will fit my bike.
 

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Discussion Starter #11
Just thought I should update the thread with the final outcome. Changing the left rotor with a (used) replacement did solve the problem!

Thanks for the help anyone
 

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bravo! now you can ride with peace of mind, nothing more terrifying than squeezing the brake lever & the bike doesn't slow down.
 

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Question for ya mate. Did you check or replace the master cylinder piston prior to changing the disks? I am having a similar problem and a few people reckon its the piston that needs replacing. Is this possible?
 
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