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Discussion Starter · #1 ·
I have a '99 Honda CBR 600 F4 that has a front brake issue, it pulsates when applied. I got the bike in a trade so I don't know what' sbeen done to it. Well I have bleed the system once. I'm sure I got all the air out, it seems everytime I pressureize the system if I roll the bike a lil it depressureizes. Does this make sense?...

TIA
 

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at the track
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You might have did something to let more air in while you were bleeding it and didn't notice it, or there is water in the fluid.
 

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Could be a bent rotor, I own the same bike and bought it after front end damage and had the same problem, found that it was the left side rotor. if at all possible take rotors off and set flat on a sheet of glass (like a counter at a shop,) and if it wobbles when you press it side to side then there's your problem.
 

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Mexican Hard Shell Taco
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Definitely warped rotors. You have to check them.
 

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rotors
 

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warped rotors would be my guess.
 

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Discussion Starter · #9 ·
I see what you guys are saying but I don't think warped or bent rotors would cause the front brake to loose pressure, right?
 

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Master Cylinder needs to be rebuilt, or warped rotors.

When you apply the brakes, does the lever come close to the bar, and then slowly get closer?
 

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Old school fool
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A pulsing feel is usually a warped rotor. Very common in cars when the front wheels' lug nuts aren't torqued down correctly. On a bike, maybe you got them too hot at some point.
 

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Discussion Starter · #13 ·
lun said:
Master Cylinder needs to be rebuilt, or warped rotors.

When you apply the brakes, does the lever come close to the bar, and then slowly get closer?
Actually there is no pressure on the brakes I have to pump the lever to get them to grab. Yesterday I was messing with the brakes and I noticed that in the view bubble for the brake fluid, there were now two little bubbles instead of just one, make sense?
 

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Might be a small leak in the system. Notice any brake fluid wetting on the lines/calipers/master cylinder?

Any of the brake pads/pistons binding?
 

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Discussion Starter · #16 ·
segue00 said:
Might be a small leak in the system. Notice any brake fluid wetting on the lines/calipers/master cylinder?

Any of the brake pads/pistons binding?
Well this weekend i'm gonna bleed the crap out of them and see if the problem goes away, if not then I'll move on to the rotors, calipers, and master cylinder.
 

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RESIDENT ASSHOLE
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If you have warped rotors the rotors will push the pads back in slightly making for the feeling of not grabbing.

If you only have to give it a squeeze or two then you know its the problem. Also your clue was that the lever pulsed in your hand. This is because the rotor was trying to push the pads back in and you were squeezing the lever. In a generic term, fluid is non compressable so you are actually feeling the pads ride against the rotor.

Pic the bike up of the ground and take the calipers off, rotate the wheel and watch the rotors. I am willing to be they shimmy and move when spun.
 

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Discussion Starter · #18 ·
hybrid said:
If you have warped rotors the rotors will push the pads back in slightly making for the feeling of not grabbing.

If you only have to give it a squeeze or two then you know its the problem. Also your clue was that the lever pulsed in your hand. This is because the rotor was trying to push the pads back in and you were squeezing the lever. In a generic term, fluid is non compressable so you are actually feeling the pads ride against the rotor.

Pic the bike up of the ground and take the calipers off, rotate the wheel and watch the rotors. I am willing to be they shimmy and move when spun.
I understand what you're saying but bent or warped rotors shouldn't cause the brakes to lose pressure, correct me if im wrong. Another thing that I tried was to go slow and apply the brake a lil to see if I could feel the warp in the rotor. It only happens when I'm at about 5mph or more, that 's why I think it has air. We'll know this weekend what's wrong with it.
 

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Warped rotors. Simply put, at higher speeds, the "feeling" of the pulsating is amplified because you are going faster and the rotor has more energy. If there was air in the brake system, you would experience brake "fade" or you would have to reapply pressure to your brake lever when stopping. You can try bleeding them (doesn't take much time) but I would start looking on ebay for some new rotors.

Good luck!
 

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Discussion Starter · #20 ·
eddie13231 said:
Warped rotors. Simply put, at higher speeds, the "feeling" of the pulsating is amplified because you are going faster and the rotor has more energy. If there was air in the brake system, you would experience brake "fade" or you would have to reapply pressure to your brake lever when stopping. You can try bleeding them (doesn't take much time) but I would start looking on ebay for some new rotors.

Good luck!
Kool i'll check it out.
 
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