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Still Fighting with front brakes
- IowaKZ
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- '80 G1 Classic
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05 Jun 2008 20:19 #218240
by IowaKZ
1980 G1 Classic
Bettendorf, Iowa
Still Fighting with front brakes was created by IowaKZ
Hey guys, I've gotten some great help with bleeding my brakes, but I still have a problem that's kind of wierd.
If I pull on the brakes, I get pressure and the bike will stop fine. However, if I hold on to the front brake (like on my sloped driveway) the front brake gradually loses pressure and eventually I roll backward.
I thought that this was still an air problem, so I kept bleeding the lines and adding new fluid while pointing the bike down the drive way. But it did the same thing pointing downhill.
then I held in the brake while in the garage, and it did the same thing.
Any ideas??
One thing I am worried about is this:
when I was putting the plunger back into the master cylinder I nicked up the 2nd rubber gasket. I am wondering if that is letting in air when I hold the front brake under continuous pressure?
Hope not, I am not sure how the seals all interact. There is no fluid leaking out and no air bubbles in the master cylinder when I open it. But I can't explain it.
would this type of thing happen just with air bubbles still in the lines?
If I pull on the brakes, I get pressure and the bike will stop fine. However, if I hold on to the front brake (like on my sloped driveway) the front brake gradually loses pressure and eventually I roll backward.
I thought that this was still an air problem, so I kept bleeding the lines and adding new fluid while pointing the bike down the drive way. But it did the same thing pointing downhill.
then I held in the brake while in the garage, and it did the same thing.
Any ideas??
One thing I am worried about is this:
when I was putting the plunger back into the master cylinder I nicked up the 2nd rubber gasket. I am wondering if that is letting in air when I hold the front brake under continuous pressure?
Hope not, I am not sure how the seals all interact. There is no fluid leaking out and no air bubbles in the master cylinder when I open it. But I can't explain it.
would this type of thing happen just with air bubbles still in the lines?
1980 G1 Classic
Bettendorf, Iowa
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- bountyhunter
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05 Jun 2008 22:27 - 05 Jun 2008 22:30 #218269
by bountyhunter
1979 KZ-750 Twin
Replied by bountyhunter on topic Still Fighting with front brakes
I remember the classic symptom of a bad master cylinder is just what you described: you can get good pressure with a fast pump, but slowly over time the pedal will go to the floor and you lose the brakes as the fluid bleeds by the piston. If the piston and seals are not holding, they will let pressure bleed off.
1979 KZ-750 Twin
Last edit: 05 Jun 2008 22:30 by bountyhunter.
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- Patton
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06 Jun 2008 03:24 - 06 Jun 2008 03:26 #218296
by Patton
1973 Z1
KZ900 LTD
Replied by Patton on topic Still Fighting with front brakes
Am thinking this repair kit would resolve the issue, but would double-check part number before ordering.
Click here > M/C Kit from Z1E
Good Luck!
Click here > M/C Kit from Z1E
Good Luck!
1973 Z1
KZ900 LTD
Last edit: 06 Jun 2008 03:26 by Patton.
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- Bluemeanie
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06 Jun 2008 06:01 #218312
by Bluemeanie
1980 KZ650F1, Bought new out the door for $2,162.98!
Replied by Bluemeanie on topic Still Fighting with front brakes
Yea, it's called bypassing. I replace many master cylinders at work because of this problem. Fluid is actually getting past the seals when pressure is held for awhile. It will stop fine but as you said, sitting with the brake on causes the fluid to be forced (slowely) past the seal. Your "nicked" seal is most likely the culprit.
1980 KZ650F1, Bought new out the door for $2,162.98!
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- IowaKZ
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06 Jun 2008 06:24 #218323
by IowaKZ
1980 G1 Classic
Bettendorf, Iowa
Replied by IowaKZ on topic Still Fighting with front brakes
Dammit:angry:
I pulled the thing out because it was so gummed up it would not slide. then I had a bear of a time getting it back in.
Will order one today and try it out.
mucho gracias!
I pulled the thing out because it was so gummed up it would not slide. then I had a bear of a time getting it back in.
Will order one today and try it out.
mucho gracias!
1980 G1 Classic
Bettendorf, Iowa
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- Patton
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06 Jun 2008 09:27 #218350
by Patton
1973 Z1
KZ900 LTD
Replied by Patton on topic Still Fighting with front brakes
IowaKZ wrote:
Perhaps a rubber cup was just "swollen," because it should not be difficult to slide either cup into the bore.
Good Luck!
...it was so gummed up it would not slide. then I had a bear of a time getting it back in....
Perhaps a rubber cup was just "swollen," because it should not be difficult to slide either cup into the bore.
Good Luck!
1973 Z1
KZ900 LTD
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- IowaKZ
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06 Jun 2008 12:17 #218379
by IowaKZ
1980 G1 Classic
Bettendorf, Iowa
Replied by IowaKZ on topic Still Fighting with front brakes
I never thought about the cups being swollen. It's possible. I took it apart and cleaned it up and tried to put it back in right away. Maybe if it had dried out some it would have fit better.
I guess to clarify a little more: I had a hard time getting it started. Once the seals were through the opening, it was easy to push back and forth.
However, getting it started was difficult. When I tried to push it into the hole, it would mushroom out and get stuck. I ended up using the shop vac to suck in the rubber gasket. However, with all my pushing and pounding before that I know I did something to the seals.
I called Z1 and ordered a new one. They said it would still ship today.
I guess to clarify a little more: I had a hard time getting it started. Once the seals were through the opening, it was easy to push back and forth.
However, getting it started was difficult. When I tried to push it into the hole, it would mushroom out and get stuck. I ended up using the shop vac to suck in the rubber gasket. However, with all my pushing and pounding before that I know I did something to the seals.
I called Z1 and ordered a new one. They said it would still ship today.
1980 G1 Classic
Bettendorf, Iowa
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