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My front discs pads are not retracting...just lock up after applying pressure to the brake handle. After a while, they retract, but not completely. I removed the calipers to see if it was a lubrication issue, but no luck. After compressing the pistons, they just tighten up again. Have bled both calipers..no change.
Having trouble finding the right service person. Any recommendations? Piston need to be replaced? Brake lines pinched?
Need help.
Thanks.........
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i had the same issue. finally just gave up and accepted the tiny bit of drag mine have. from what i gather, the o ring that seals the piston will fail and you will need to replace them, also gunk builds up behind the piston and will keep it from retracting. is the return hole plugged up in the cylinder? that is a good possibility.
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Administrator
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This is usually caused by the master cylinder not working properly. To test for this, just wait until the brakes are dragging, then loosen the bleeder. If the brakes release, it is the master cylinder. If not then it is the caliper, but my money is on the master cylinder.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Tried opening the bleed valve while the front brakes were locked on...no change. Guessing it's something with the calipers. FYI...the bike is a 1981 model with 23,000 miles. I've owned since 1984. I don't ride much, and the bike has always been garaged.
Thanks.
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How do the lines look? Sometimes when they get old they can swell and cause problems such as this.
It's only illegal if you get caught.
If at first you don't succeed, use more lighter fluid
95% of Harley Davidsons ever made are still on the road... The other 5% made it home.
New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"
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Lines look OK with a quick visual...no bulges or leaks.
Thanks
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Administrator
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Sounds like dirty caliper pistons. You may or may not need a rebuild kit.for the calipers, but considering the age, your rubber bits are probably not all that great.
The caliper pistons may just be dirty, but they're most likely corroded. A disassemble and inspection is all you can do at this point. You might be able to clean/sand/polish the pistons back to useable condition.
Before you go too far start looking into rebuild kits and replacement pistons. For whatever reason an '81C is hard to find parts for.
If you end up need a piston or two shout at me. I have a couple pristine ones out of an old '81 C front end I couldn't use when I came up short on my hunt for brake parts.
Good luck buddy.
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Administrator
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Actually, let me rephrase that last part before someone calls me on it :)
I did in fact find the parts. But they are not in the affordable, readily available kits like you will find for the K and F models.
I found every part as individual part numbers from different dealerships. Due to the prices I was given I didn't even check in to availability of the parts, so you still may or may not actually be able to put.your hands on them. But they did find the.parts listed.
All said and done with all new rubber bits and a few pistons I was looking at over $350 and that was not factoring in shipping.
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Thanks, Shiny. I can remove the calipers from the forks, but not sure how to proceed from there. Can I disconnect the brake lines from the calipers, or should I work on them connected? I don't mind tinkering a bit, but I know my limits.
Again, thanks for your kind advice.
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Administrator
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If you plan to completely disassamble the claipers I'd leave the brake lines attached at first. That way you can pump the brake lever and it will push the caliper pistons out of the caliper for you. Wrap it all in a rag if you do this as when the pistons pop out it will kinda squirt fluid out. There's not a lot of pressure here,unless something is stuck, so you don't have to worry about them flying out across the room.
If you do seem to have to apply a lot of pressure to the lever just go nice and easy until they pop out. Don't overdo it.
Bolting the calipers back on to the forks at this point will make it easier to get the banjo bolts loose that hold the brake lines to the calipers. They're usually pretty tight and it's hard to grip those tiny calipers by hand while you do this.
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OK. Thanks. I'll let you know how it goes..when I can find time to do it.
Appreciate the advice.
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Took the bike for maybe the last ride of the season here. Front brakes got really tightened on the rotor. Tried bleeding again...both calipers. Now, calipers really clamped so hard that I cannot move the front wheel at all. This is something new. Haven't had a chance to remove the calipers yet. Does this indicate something else?
Appreciate advice.
Thanks
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Administrator
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Rusty/corroded calipers. However the good news is, since the pads keep pinching the rotor harder, you might not have too much trouble getting them, and the pistons out of the caliper.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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...if I can get the calipers off the rotors. Film at eleven!
Thank you.
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Administrator
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 Haha! Good luck bud,you can do it.
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Administrator
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My '79, I've had to knock them down twice already.
For some reason, dusty gravel roads seem to put a fine grit
around the pistons.
They then get tight, squeal a bit and start to drag.
Which is kinda dangerous when turning.
I had a front washout on a Kawasaki Mach 3,
back in High School, because I was too lazy to
clean the front brakes.
They were dragging, I was pushing it, and that tight hairpin 300 yards from my driveway got me.
Knock'em down, clean everything, if the pistons aren't rusty, I'd reassemble and see what's up.
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OK....might be easier to drop the front wheel to work on the calipers....or would it?
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Administrator
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You need to remove the calipers in order to get the wheel off.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Administrator
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 maybe take the 2 big allen bolts out that secure caliper to fork,
open the bleeders to get any hydraulic pressure off,
get a rubber mallet and gently wack them top, then bottom, kinda forcing them to slide off the disc.
gently, but firmly.........
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OK. Got the calipers off...rubber mallet helped. A few questions. There are two recessed cap screws on the inside part of the caliper (facing the wheel). I'm guessing these hold the caliper together. Correct? Also, to remove the pads...there are two pins that seem to hold the pads on. Do I need to remove those pins? Next, pumping the brake handle to remove the piston...can I do one at a time, or do both pistons have to be removed at the same time? Once the pistons are out, can I remove the calipers from the brake hoses to work on them?
Appreciate your help. As you can tell, I'm a little new to this.
Thank you kindly.
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