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Sticking front brakes

Started by Waiex191, October 18, 2023, 09:05:16 AM

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Waiex191

Thought I had my brakes sorted. Pulling up to a stop this morning and they wouldn't release. After I was completely stopped and hands off they released. Thought it could be a bulky glove fumble issue, so tried it again on the airport driveway. Same.  I had a lot of trouble rebuilding the FZ1 master and I'm thinking that is probably the issue. New brake lever and the pivots are clean and lightly greased. Plan to order new brake lines. I don't think that is the issue but want to cover the bases. May try sacrificing a chicken at midnight or something too.  Would like to hear any thoughts the gang may want to share.
Bryan
1989 FJ1200
1981 Suzuki GN400
Poplar Grove, IL
 

balky1

Overfilled container can get the brakes sticking after riding (when hot) and releasing again after cooldown because the fluid has no space to expand. I made the mistake once.


FJ 1100, 1985

Motofun

Also make sure your brake lines are routed so as to not cause a pinch.  A crimp in the line will allow high pressure forward flow but reduce low pressure back flow to the reservoir.
'69 Honda Trail 90
'75 Honda CB400F
'85 Yamaha RZ350
'85 Yamaha FJ1100
'89 Yamaha FJ1200
'09 Yamaha 125 Zuma
'09 Kawasaki KZ110 (grand kids)
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'14 Yamaha FZ-09
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'23 Yamaha Tenere 7
SOLD: CBX,RZ500,Ninja 650,CB400F,V45 Sabre,CB700SC,R1

fj1289

Quote from: Waiex191 on October 18, 2023, 09:05:16 AM
Thought I had my brakes sorted. Pulling up to a stop this morning and they wouldn't release. After I was completely stopped and hands off they released. Thought it could be a bulky glove fumble issue, so tried it again on the airport driveway. Same.  I had a lot of trouble rebuilding the FZ1 master and I'm thinking that is probably the issue. New brake lever and the pivots are clean and lightly greased. Plan to order new brake lines. I don't think that is the issue but want to cover the bases. May try sacrificing a chicken at midnight or something too.  Would like to hear any thoughts the gang may want to share.

New brake lever - Yamaha or aftermarket?

Waiex191

Thanks guys for the replies. I didn't overfill when I bled the brakes. Should be space and this was just after startup, 34F outside, night in the garage probably around 50F.

I have not changed the line routing, but I'll check. Could be related to fork dive.

Aftermarket brake lever.
Bryan
1989 FJ1200
1981 Suzuki GN400
Poplar Grove, IL
 

Old Rider

I guess you have checked that the returnhole in the resevoir is open. also the atmosphere pressure hole in the lid of reservoir.If overfilled the brakefluid will come out there. im not sure but if that atmosphere hole is not open it may pressurize the brakes.

Waiex191

Quote from: Old Rider on October 19, 2023, 02:07:34 PM
I guess you have checked that the returnhole in the resevoir is open. also the atmosphere pressure hole in the lid of reservoir.If overfilled the brakefluid will come out there. im not sure but if that atmosphere hole is not open it may pressurize the brakes.
I definitely made sure the return hole in the reservoir is open when I rebuilt it before.  Everything was clean and had liters of brake fluid flushed through it.  I did not think there was a hole from the reservoir to the atmosphere though.
Bryan
1989 FJ1200
1981 Suzuki GN400
Poplar Grove, IL
 

Old Rider

I mean the tiny passage in the lid that make the rubber diaphragm move down when brakefluid level is sinking. Im not sure if it can make the brake
binding if it is clogged bith worth a look if it clogged. As im sure you know there are 2 holes down in the reservoir one is very tiny check that both holes are open use a tin brass wire to poke it open if clogged

joebloggs

Quote from: Waiex191 on October 18, 2023, 09:05:16 AM
Thought I had my brakes sorted. Pulling up to a stop this morning and they wouldn't release. After I was completely stopped and hands off they released. Thought it could be a bulky glove fumble issue, so tried it again on the airport driveway. Same.  I had a lot of trouble rebuilding the FZ1 master and I'm thinking that is probably the issue. New brake lever and the pivots are clean and lightly greased. Plan to order new brake lines. I don't think that is the issue but want to cover the bases. May try sacrificing a chicken at midnight or something too.  Would like to hear any thoughts the gang may want to share.

I'd try to locate the problem before throwing money at rebuild kits

Wrap some cloth around the top banjo and back the bolt out a few turns to release the pressure, then remove the bolts holding the caliper to the fork leg. If the calipers are free rebuild the master cylinder, if not pull the calipers and check the pistons are free.
1989 3CV

fj1289

I had an aftermarket lever do the same to me many years ago.  It didn't allow the master cylinder to fully retract and would build up pressure and lock the brakes up.  If I remember correctly I had to file a bit off the lever to allow the master cylinder to fully retract and release pressure. 

Waiex191

Thanks for the continued replies. Joe, the brakes release when the stop is done, and the forks decompress. So I can't crack the banjo to release pressure. I'll check the lever too.
Bryan
1989 FJ1200
1981 Suzuki GN400
Poplar Grove, IL
 

Old Rider

Have you fixed it? if not i have more test you can do .Jack the front up so the wheel spins in the air. Does it spinn freely ? if not try to losen the caliperbolts
and spin again then while the wheel is spinning use the frontbrake lever and stop the wheel several times.Then while wheel is spinning tighten the caliperbolts
losely one by one and check if it is binding. I have once had a sticky frontbrake (and wheel) that turned out to be misangled forks and one fork was sitting about 2mm higher in the triple tree.If that is the case losen all bolts wheel bolts and axle clampbolts to exept the upper forkclamps and bounse the front down some times to get the forks to angliment.

Waiex191

Not yet. I removed the clips that hold the brake lines to the fender mount bolt, to see if that was causing an issue. Definitely related to fork compression. A gentle stop is no issue. A hard stop will make them stick until it stops and the forks rebound.

New stainless braided lines are on the way from RPM.  I was due for new lines anyway - ask Pat!
Bryan
1989 FJ1200
1981 Suzuki GN400
Poplar Grove, IL
 

balky1

Hmmm... Is the anti-dive still connected? I don't see how it could be related but the fact that they unstick on fork rebound makes me wondering.


FJ 1100, 1985

Waiex191

Quote from: balky1 on October 30, 2023, 09:40:15 AM
Hmmm... Is the anti-dive still connected? I don't see how it could be related but the fact that they unstick on fork rebound makes me wondering.
There is no anit-dive on my '89.
Bryan
1989 FJ1200
1981 Suzuki GN400
Poplar Grove, IL