HELP!! what causes brake pressure not to release?

[donnelly317]

Other than sliding pins what would case brake pressure not to release in front brakes? I have FZR 6 pots with Nissin master...

Good thing I was only doing 30 because my front brakes didn't release after tapping brake... I can't duplicate it. It sucked getting it off the road it wasn't fun!!!
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[Karmakatt]

"Remember Conan.. What doesn't kill you.. Makes you stronger..!!"

I'll bet your twice as strong than before the incident!! Sounds like you weren't injured.. Luckily!!
I'll follow this one for sure..
Must have been a push/pull/tugging movement..


KarmaKatt
VMOA 5652

 

[Fire-medic]

A plugged small hole in the master cylinder (the forward hole, closest to the banjo bolt). You have crud in your fluid if it's getting plugged, your system needs a thorough cleaning and flush a couple of times. Use a straight pin to poke-clean the hole. If you don't at-least flush the system, the same problem is going to re-occur. I would remove the hoses and check them for being unobstructed.

Or, a collapsed hydraulic line. They can look fine outside, but collapse inside and act as a 'one-way' valve, building pressure but not releasing it.

Those are the most-common causes.

If you don't see the "little fountain" from the small hole when you squeeze the brake lever w/the cap off (guard your bodywork and bike) where fluid shoots-up a couple inches depending on how-quickly you squeeze, and how-far, it's plugged.

 

[twistedmax]

I've had internally clasped lines cause that, if it does it again you can open the bleeder and it may allow the pressure to equalize so that you can at least move the bike easier. I'm with FM , clean everything and replace the hoses.

 

[donnelly317]

Yes I was wondering about hoses.. I broke the bleeder it release.. now I have proof to show the girlfriend that I need to buy blue braided Galfers for the front .

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[Miles Long]

I had a 'closer to God" moment a few years ago, while traveling at 110 kph on the superslab in Quebec.... all going well, hadn't used either brake in some time.....all of a sudden, the front brakes seized completely, the bike slowed on it's own, from highway speed to a complete stop in no more than 15 seconds, I had no idea what was happening (my buddy following thought I had blown the motor, all he could see was white smoke)...as luck would have it, I managed to get the bike stopped in a small traffic island, formed where an access road joined the highway, very nearly dumping it in the process. The brakes were completely locked, two of us could not push it to the shoulder of the road. So we waited, for about 20 minutes, while traffic wized by on the highway on one side and the entry road on the other.
Eventually, the calipers, rotors, and fluid cooled down enough so that the bike would move with both of us pushing, and we got it on the side of the road. Then I looked for the cause. Turns out there was no play at all in the front brake lever, the bolt adjuster was in constant contact with the hydraulic plunger. The locknut had apparently come loose, and over the course of the morning the bolt had gradually worked it's way forward, effectively applying the brakes without the lever being pulled. Eventually the heat generated by the stuck calipers/rotors had heated and expanded the brake fluid, eventually traveling back to the master cylinder, and siezing everything up.
After adjusting and LOCKING the lock nut in it's proper position (to allow a bit of clearance before the bolt hits the piston), the brakes worked fine, and I haven't had any problems since. However, I do find myself checking the lever for free play every once in a while, while riding the bike.
Cheers!

 

[donnelly317]

Thanks for the massive write up! But I don't have a bolt adjuster on the nissin masters. Don't think that your write up went to waster someone may search for brake problem find this thread and use it! Lol thank you tho! :thumbup:

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[MaxMidnight]

The point to take from Miles' post is that you should also check that there isn't anything impeding the m/c piston returning which will cause the pressure to remain in the line.

 

[donnelly317]

AHHH YES YES. Thats the first thing i checked second was the slide pins on calipers. I did just put new aftermarket levers on but i looks there now pushing in piston. Also one i got it off road i pumped it a few time it built up more and more pressure untill i couldnt pump it anymore.

 

[Traumahawk]

Well it wasnt the lines then but it still wouldnt hurt to change them to steel braided. I believe the service manual says to change the stock brake lines every 5 years.

 

[donnelly317]

Ding dong!! Emailed sean to get prices on galfers but a lot explained to him my problem. Totaly forgot to mention something here. My resivior looked over full so I removed some fluid... sean said its resivior it to full and fluid heats up it could cause the hyd lock! I think we may have a winner.

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[Fire-medic]

I just met another forum member & checking-out his bike, saw the locknut at the master cyl gave him about 3/4" or > lever travel before the brake initiated. I suggested that a prudent adjustment would allow his lever not to travel that far, and would feel like better braking. He wouldn't have any of it, maybe he was a veteran of the 'wandering-locknut' syndrome?:ummm:

I think the Russell SS lines may be less-$$ than the Galfers. I have also used Earl's on other bikes.

 

[donnelly317]

I had a 'closer to God" moment a few years ago, while traveling at 110 kph on the superslab in Quebec.... all going well, hadn't used either brake in some time.....all of a sudden, the front brakes seized completely, the bike slowed on it's own, from highway speed to a complete stop in no more than 15 seconds, I had no idea what was happening (my buddy following thought I had blown the motor, all he could see was white smoke)...as luck would have it, I managed to get the bike stopped in a small traffic island, formed where an access road joined the highway, very nearly dumping it in the process. The brakes were completely locked, two of us could not push it to the shoulder of the road. So we waited, for about 20 minutes, while traffic wized by on the highway on one side and the entry road on the other.
Eventually, the calipers, rotors, and fluid cooled down enough so that the bike would move with both of us pushing, and we got it on the side of the road. Then I looked for the cause. Turns out there was no play at all in the front brake lever, the bolt adjuster was in constant contact with the hydraulic plunger. The locknut had apparently come loose, and over the course of the morning the bolt had gradually worked it's way forward, effectively applying the brakes without the lever being pulled. Eventually the heat generated by the stuck calipers/rotors had heated and expanded the brake fluid, eventually traveling back to the master cylinder, and siezing everything up.
After adjusting and LOCKING the lock nut in it's proper position (to allow a bit of clearance before the bolt hits the piston), the brakes worked fine, and I haven't had any problems since. However, I do find myself checking the lever for free play every once in a while, while riding the bike.
Cheers!

Ok you guys im a dumbass. I told ya miles someones gonna look at it and it will help them out. Well it was this guy. My new levers were pushing in plunger just ever so slightly!!!!!!! Little grinding it will be all fixed this weekend!

The point to take from Miles' post is that you should also check that there isn't anything impeding the m/c piston returning which will cause the pressure to remain in the line.

I looked didnt think anything was wrong till today when I took off my lever im stupid you guys were right all along!!!

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[bazwell]

I'm glad you seem to have found it.
Apart from all the advise given already, dirty/sticky/corroded pistons in the caliper can cause the similar symptoms, but it's not so likely.

 

[Traumahawk]

Just glad that you found out what the problem was.

 

[donnelly317]

Me too thabks guys!!!! Now I can't get my braided lines though damit!!! Welk atleast I could use that money for the dyno!

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