Topic: Front Brakes Stick and won't Retract

[clarkjh]

If the wobble in the rim is bad enough to transfer to the hub at speed, I don't think I'd have the gonads to ride it.

And I'm no expert just a "Jack of all trades, and Master of none."

James

[81cb650C]

The wobble wasnt all that bad  maybe 1/4 " at the rubber but it definetly solved my problem.  I dont know, it could have solved another issue that i wasnt aware of but i truely think the the rim was the problem. 

[UnCrash]

This is a great thread!

I'm contending with a front brake that's sticking on my 78 750F.  I believe that I have multiple problems...  I'm going to ream out the little hole in the MC first thing in the morning (great tip!).

I learn best by taking things apart to see how they work.  The sticking brake perplexes me a little.  With the brake off the rotor and dangling in the air, if I squeeze the brake lever, the piston comes out but doesn't go back.  So I squeezed the lever more, the pison comes out more...

I couldn't get the piston to go back when squeezing it with a big pair of pliers so I opened up the bleeder valve.  I found the little hole in that completely blocked up so cleaned it out.  With that off fluid was able to come out, but I still couldn't squeeze it back.  I got out a C clamp and sunk it back in with the bleeder off. 

This makes me think that I've got some blockage that's preventing fluid from getting back to the resivoir.

I'll get the guitar strings going tomorrow.

THanks for the great info.

Cheers,

Ben

[mrbreeze]

This is a great thread!

I'm contending with a front brake that's sticking on my 78 750F.  I believe that I have multiple problems...  I'm going to ream out the little hole in the MC first thing in the morning (great tip!).

I learn best by taking things apart to see how they work.  The sticking brake perplexes me a little.  With the brake off the rotor and dangling in the air, if I squeeze the brake lever, the piston comes out but doesn't go back.  So I squeezed the lever more, the pison comes out more...

I couldn't get the piston to go back when squeezing it with a big pair of pliers so I opened up the bleeder valve.  I found the little hole in that completely blocked up so cleaned it out.  With that off fluid was able to come out, but I still couldn't squeeze it back.  I got out a C clamp and sunk it back in with the bleeder off. 

This makes me think that I've got some blockage that's preventing fluid from getting back to the resivoir.

I'll get the guitar strings going tomorrow.

THanks for the great info.

Cheers,

Ben

If you couldn't retract the piston with the bleeder open,your problem is in the caliper.yor piston is hanging up......corrosion,bad seal,etc. You should address that before the comp. port in the master.

[francisew]

Speaking of bearings... how much trouble is it to replace the wheel bearings? I'm pretty sure that my '83 cb650 sc bearings deserve changing, and I do a LOT of highway driving, so this might make life more pleasant. Is a bearing change something I can do on my own? How much should bearings cost?

Thanks,
Francis

(On Saturday I changed my brakes, and heard squeaking noises afterwards. I thought it was because the rotors might be bent. Yesterday night I measured them, and they seem ok, as does the wheel rim. I think the squeaking is just the new brake pads, FA69 type, resurfacing the rotors. Now I'm thinking the bearings deserve an overhaul...)

[krusty]

Before doing anything,you should make sure the tiny passageway in the bottom of the reservoir is not blocked.If it is,your brake will not release.Take the cap off of the master cylinder.You should put a sheet of plastic underneath before doing this to prevent spilling brake fluid on painted surfaces. Down in the bottom of the reservoir are 2 holes. The tiny one (compensating port I believe it is called) is the one you after. Take a #1 guitar string (the real fine one) and run it in & out of that hole.Then gently pump the lever to see if you get any action.Don't reef on the brake lever with the cap off or you will squirt brake fluid all over. This may or may not be the cause of your problem but is the easiest thing to check first.

Just completed dual disc conversion and found front pads weren't releasing. Read the above and by co-incidence I had a broken #1 string on one of my guitars. Two minutes later and the hole was clear. I'm also using silicon brake fluid cos I've experienced what the other stuff does to paint and calipers. Thanks for the tip.

[Brixie387]

Rainmaker, thanks for the step-by-step directions.  I just bought a CB500 after 13 years without owning a bike, so I was a little nervous about my first do-it-yourself repair, but I just rebuilt the front caliper using your tips and it went perfectly - no more sticky brake!

[HS]

So I've been working on the front caliper like an elf at Christmas.  Inside it's all shiny.  I took a brass brush on a dremel to the groove inside the caliper, where the o-ring seats, and cleaned it out.  Looked in with a small mirror...it's spotless.  My question is, the o-ring looks to be in pretty good shape but it sits outside of the groove just a smidge....almost seems to be higher on one side...the oring that is.  I can get the piston that's in great shape in the caliper, but I have to press it in, even when there's brake fluid on the piston.  The piston will not fall out on its own.  I fear it will bind when I put it all together.  Do I need a new o-ring or is the piston always under some pressure not to come out of the cylinder easily?  I'm new to these things and I'd really like to get it right the first time.

On to rebuilding the master cylinder now...

HS

[MCRider]

So I've been working on the front caliper like an elf at Christmas.  Inside it's all shiny.  I took a brass brush on a dremel to the groove inside the caliper, where the o-ring seats, and cleaned it out.  Looked in with a small mirror...it's spotless.  My question is, the o-ring looks to be in pretty good shape but it sits outside of the groove just a smidge....almost seems to be higher on one side...the oring that is.  I can get the piston that's in great shape in the caliper, but I have to press it in, even when there's brake fluid on the piston.  The piston will not fall out on its own.  I fear it will bind when I put it all together.  Do I need a new o-ring or is the piston always under some pressure not to come out of the cylinder easily?  I'm new to these things and I'd really like to get it right the first time.

On to rebuilding the master cylinder now...

HS

I was schooled on the ORIng here some time ago, and have forgotten the specifics. IIRC it does sit a little crooked in the groove. That's so when the piston goes towards the disc the ORing flexes. When the pressure is relieved the flex in the ORiing draws the piston away from the disc. That is the ONLY thing drawing the piston back. The fluid simply retreats when the lever is released, the ORing actually moves the piston away from the disc. ANd only about 5-8 thou at that.  The piston should not move freely if installed onto the ORing. For reason already stated.

[HS]

So I've been working on the front caliper like an elf at Christmas.  Inside it's all shiny.  I took a brass brush on a dremel to the groove inside the caliper, where the o-ring seats, and cleaned it out.  Looked in with a small mirror...it's spotless.  My question is, the o-ring looks to be in pretty good shape but it sits outside of the groove just a smidge....almost seems to be higher on one side...the oring that is.  I can get the piston that's in great shape in the caliper, but I have to press it in, even when there's brake fluid on the piston.  The piston will not fall out on its own.  I fear it will bind when I put it all together.  Do I need a new o-ring or is the piston always under some pressure not to come out of the cylinder easily?  I'm new to these things and I'd really like to get it right the first time.

On to rebuilding the master cylinder now...

HS

I was schooled on the ORIng here some time ago, and have forgotten the specifics. IIRC it does sit a little crooked in the groove. That's so when the piston goes towards the disc the ORing flexes. When the pressure is relieved the flex in the ORiing draws the piston away from the disc. That is the ONLY thing drawing the piston back. The fluid simply retreats when the lever is released, the ORing actually moves the piston away from the disc. ANd only about 5-8 thou at that.  The piston should not move freely if installed onto the ORing. For reason already stated.

Very helpful, MCRider...I feel a lot better.  Thank you!

HS

[Terry in Australia]

Yeah mate, what Ron said, the piston is a very tight fit in the bore, I just rebuilt 2 GL1000 calipers with new pistons and seals, like you I scraped all the gunk outta the grooves and the O ring sits slightly proud of the cylinder, making it pretty tough to install the new pistons. Cheers, Terry.

[HS]

Thanks, Terry.

The master cylinder is rebuilt...that was a gem...LOL.  Slingshot Cycles shipped the brake lines so I should be golden.

I haven't touched the rear drum.  Bike only has 6800 miles on her but she hasn't been ridden much over the years and it shows.  I was thinking of testing them once she's running and going from there.  If anyone has a compelling reason for going ahead and cracking open the rear brakes now, please lemme know.

HS

[Macmorgan]

After rebuilding a bunch of master cylinders and calipers on Honda's, Yamaha's, BMW's, even Bultaco Streaker, I found that a .009 guitar E string chucked up in a pin vice got the small return hole cleared out. Also works well on the 400/4 carb. Jets.

[daveybaker]

Unclogging the tiny return hole with a teensy piece of wire worked for me. Only took 5 min!

[RAFster122s]

Zombie thread being resurrected... Not a bad thread to bring back to life....

[JerrodR]

I just put new pads on mine, and it was sticking for a moment, and then retracting. I had to remove the plunger pad, and grind the perimeter down I'd say about a thousandth's of an inch and reinstall. It works fine now.