Front brakes...





#1
I just put a new set of socks on the bike.  A set of Avon Vipers.  After I had the front tire on, I pumped the front brake and the lever came up normal.  If I move the bike at all, forward or reverse, I lose lever pressure, it goes right to the bars like there's air in the line.  Checked that, no air, plenty of fluid.  I haven't had a chance to have a look at it yet, but when I do, I want to be able to go the problem, and fix it, because I won't have a whole lot of time then either. I've tried riding it, to see if it would come back to normal but it doesn't, if I pump the lever 2 or 3 times it comes up right away, but as soon as I release the lever to move again, it goes to the bar again...2-3 pumps..back up...move.....goes away again.

Anyone ever experience this before.  I never did anything different than I have done a dozen times with this bike.  I just unbolted the calipers(left the lines connected), replaced the tire, and rebolted everything back on.  
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#2
You have air in the system. remove the cover on the resevior with the rubber. Top it up if necessary. crack the bleed screw on the left caliper just enough to allow you to pump the lever without fluid comming out. Hold the lever tight and loosen the screw. Let the fluid drain keeping an eye on the resevoir, to keep it topped up. Lock the bleed screw and repeat a few times untill no air bubbles are seen. repeat on the right side. If the problem still persists then your seals need to be replaced. but this is unlikely, i think it simply air.....
 
#3
Thanks, it's probably the master cylinder, there's no air in the system,  I've checked it a couple of times, and there's no evidence of a leak at any of the seals. All I did was replace my front tire. I was just checking to see if this was a common problem with the early Busas.
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BigBSBusa

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#4
Not sure it's an air problem. I would check your caliper and make sure the pads are seated correctly. Just my $.02.
 

SpeedAdict

Gabe
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#5
If you took your rotors off make sure you put them on the same way and tight. A warrped rotor or loose rotor would cause the same problem.
 

Sloto200

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#6
if your going to be bleeding the brakes you might as well think about changing out the fluid unless you have done that recently. If its a 99 and the fluid is origninal it needs to be changed IMO. Good luck with it!
 

runeight

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#7
this is a long shot to say the least.

When you torqued the calipers did you spin the front tire and apply the front brake a couple of times? Floating calipers.

Did you compress the front forks before torqing the pinch bolts?

Sounds like the pistons recessed into the caliper a little. I would take the advice of others and completly bleed them out with fresh fluid.

Chalk it up to Murphy's Law.

runeight...
 
#8
Thanks for your responses.  I'll change out the fluid again, and see if that solves the problem.

Yeah, runeight, it feels like one of the pistons is receding into the caliper everytime I move the bike.  They come up to feeling just like normal as long as I'm stopped.  2 pumps and they're up while moving, and if I keep pressure on the lever while riding, it'll stay up.

My rotors are true and torqued properly, and in the proper direction of rotation.  I've done this several times in the past, and on countless numbers and kinds of bikes, but this is the first time I've experienced anything like this.

Once again, thanks, folks.
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#10
I pulled the calipers, and changed out the fluid.  There was one inner piston sticking on both calipers
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.  It's back to normal now
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.  Stainless is going to be my next mod, I think.
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Thanks for the reponses.
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#11
You have air trapped in the banjo fitting right at the reservoir. It is usually impossible to force air from that location all the way down to the calipers. You need to bleed that location just like you would a caliper except you loosen the banjo bolt instead of an opening a regular bleeder.
 
#13
Thanks strange, unless I misunderstood your post it doesn't fit the symptoms. If the piston were sticking in the retracted position the brake would not engage and if it were sticking in the extended position the brake would not release. Having to pump the lever each time you use the brake would indicate air trapped in the system. Pumping the lever will compress the air enough to push the piston out but once the brake is released the air expands again. Perhaps the air was removed the second time around.
Bleeding from the caliper end works best on most systems but on a bike air can still be trapped the top of the banjo fitting.
 

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