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Discussion Starter · #1 ·
ok my 09 sv650 with 05 gsxr 600 front end has a crazy pulsing in the brakes. I did a run out test on the rotors. they are straight. pulled the wheel off and check the wheel. its good. changed the fuid. its new. pulled to rotors, and caipers off, checked them and torqued them properly.

also if the bike sits for a week or longer the breaks have to be bled of air in order to work properly.


Someone have an idea?
 

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Pulsating brakes is almost a sure sign that you have some warping or some kind of buildup in the rotors.

However, the larger issue here is the encroachment of air into the system. You really need to find that leak and get that fixed before you worry about the pulsing (and one problem may fix the other).

Inspect the reservoir, the reservoir tube, the master cylinder, the brake lines, the calipers and bleed screws to try and nail down the source of the leak. Pull the pads and check the pistons for any sign of wetness. They should be dry.
 

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if there are no visible signs of a leak the master cyl may be leaking internally- that is the fluid may be coming backwards past the seal, so it's still all inside the reservoir but air and fluid are swapping places inside the master cyl. bleeding works for a little while but each time you remove the cap to add fluid you let in some more air so the cycle can continue.
 

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Maybe double check the rotors for warp. It is hard to get pulsation with straight rotors.

2nd clue: Warped rotors can make if feel like there is air in the system, even when all is OK. A wave in the rotor will push the caliper pistons in farther than normal, requiring lever pump to bring them back out. It is just like having to pump the lever after a simple pad change; when you push the pistons in to make room, they need to be pumped back out into position.

Clue #3: Is there any evidence of raw brake fluid on the lines/calipers/master/banjos?
 

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Discussion Starter · #6 ·
I just dismantled the brakes, checked the lines, banjo bolts, pads, pistons, master cylinder, etc. Put it all back together and filled with new fluids. Everything looked good. We will see how it works.

I forgot to mention something. If i ride the bike and then park it the brakes require no pumping to get back to feeling right. Then if the bike sits the brakes get soft. If i bleed them after i park it then they never get soft. We will see what happens from here.
Sent from my DROID RAZR using Motorcycle.com Free App
 

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You say the brakes get soft...

Are you talking about excessive lever travel or sponginess?

When you have this softness, if you rapidly pump the lever, does the softness go away?
 

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if there are no visible signs of a leak the master cyl may be leaking internally- that is the fluid may be coming backwards past the seal, so it's still all inside the reservoir but air and fluid are swapping places inside the master cyl. bleeding works for a little while but each time you remove the cap to add fluid you let in some more air so the cycle can continue.
+1. Sounds to me like the master cyl is going bad. Warpage is pretty easy to check by spinning the wheel and measuring the runout. If it is good...yet still pulsing....you've got something on the rotor, either contamination or brake pad material unevenly bedded. Scotchbrite them real good until shiny and re-bed should take care of the pulsing. Rebuild or replace the master to fix the sponginess.
 

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For some reason, I thought it was possible to get some sort of pulsing in the braking system due to something in the forks. I can't remember what exactly what it was but something with oil or springs. Am I making this up?
 
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