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I rebuilt mine and found that it was fairly straight forward. You need the manual of course and keep everything absolutely clean. You most probably will need a source of compressed air to get the pistons out of their bores and pay attention to the warning that they will come flying out. Cover the pistons with a doubled up rag and then zap air thru the fluid inlet.

When reassembling get all the components totally clean like new. Then be dead certain that all the seals and o'rings go back into the correct places and are oriented correctly. Lube the pistons and seals with a bit of brake fluid like it says. Use a torque wrench. Use new aluminum sealing washers under the banjos as required.

As long as you have them apart consider installing Speedy Bleeders. They make the brake bleeding chore much less hassle. Be sure that the entire system has been emptied of old fluid. Flush it out with new brake fluid top to bottom, including the master cylinder. Bleed the MC first and keep an eye on the reservoir.

Remember that brake fluid is nasty stuff and will take off paint and is really bad if you get it in your eyes so be careful.. There was a thread here lately about a guy that was having the devil of a time getting his brakes bled and had used a whole can of fluid wiith no results. I find that a whole can just begins to get the system flushed out of air and it takes two cans to get the job done. Never try to save fluid once the seal on the can has been broken. That's false economy as brake fluid is very hydroscopic meaning that it absorbs water right out of the air and that is a bad thing.

All of the above being said, I do know folks that just can't seem to rebuild calipers without encountering major problems. I think it is a matter of being extremely fastidious, keeping everything super clean, and being willing to use lots of BrakeKleen type stuff, Q tips, and lots of paper towels, not shop rags.

BTW, I swear by Maxima Racing fluid.
 

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yes I will... make sure you don't think "the fucking service manual's wrong" when you spend 1/2 hour looking at the seals and can't see the bevel that the service manual shows. They ARE uni-directional!


The manual makes it look like there's this huge, obvious bevel on 'em. There's not. It's hard as hell to see. But it's there. learn from my idiocy. I thought it was a misprint.

Oh - and as far as pushing the pistons out... it makes life alot easier if you try to extend the pistons as far out as they'll go (without completely popping out) before removing the brake lines. I usually pull the one caliper off the forks (leave the other mounted for now), remove the pads, and then pump the brake lever to extend the pistons out close to as far as they'll go without completely popping out. You have to use your fingers to hold the ones that want to come out easiest so that the 'hard budgers' will extend. When each piston is out about the same amount, and close but not at the point where they'll pop out, I stick a piece of wood or a single pad in between them to keep them from extending any further, pull off the other caliper, and do the same. Then remove the brake lines, drain the fluid, and pull the blocks out. If you do it right, they'll be loose enough to pull right out of the bores without the use of any air pressure.

 

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Discussion Starter · #6 ·
Thanks guys. The problem seems to be that one of the pistons is stuck (won't push back). Perhaps I'll keep my eyes open for a used caliper or calipers, swap them and then try the rebuild so I'm not fucked if I can't get it right.

Anyone got a set of 4 pots lying around?
 

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Thanks guys. The problem seems to be that one of the pistons is stuck (won't push back). Perhaps I'll keep my eyes open for a used caliper or calipers, swap them and then try the rebuild so I'm not fucked if I can't get it right.
Sometimes the dust seals get twisted and bind the piston up. Or it could be just alot of grunge coating the surface of the piston. If it's just one piston that's giving you trouble, what you can do is pull the caliper, pull the pads, use your fingers to hold the three other pistons in place, and pump the brake lever (sloooowly) to pop just that one stuck piston completely out of the caliper (do this, of course, over a bowl to catch all the fluid). From there, you can inspect the piston and seals. If none of them are damaged, clean the seals, clean the piston with a nylon brush & brake fluid, coat all in brake fluid, reinstall the seals, push the piston back in, and refill & bleed.
 

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There was a thread here lately about a guy that was having the devil of a time getting his brakes bled and had used a whole can of fluid wiith no results. I find that a whole can just begins to get the system flushed out of air and it takes two cans to get the job done.
For real? I only use like 3/4 of a bottle of Motul 600 when I drain and refresh my brakes. Never had a problem with needing to re-bleed and brake lever is rock hard after zip tieing overnight. Anyone use that much fluid?
 

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There was a thread here lately about a guy that was having the devil of a time getting his brakes bled and had used a whole can of fluid wiith no results. I find that a whole can just begins to get the system flushed out of air and it takes two cans to get the job done.
For real? I only use like 3/4 of a bottle of Motul 600 when I drain and refresh my brakes. Never had a problem with needing to re-bleed and brake lever is rock hard after zip tieing overnight. Anyone use that much fluid?
Sometimes I can get it done with just 3/4ths of a can as well. Especially if it is just a drain and refresh deal, and I do get a rock hard lever as well. But, there are those times when it takes a lot of fluid to replace what you have drained like when you completely rebuild the whole system.. I believe that since he was talking about doing the whole deal, ie pistons out, lines off full drain etc, that it wouldn't be all that unusual to use a whole can and a bit of a second. Maybe I should have said that I use just a bit of the second can. But, I'll agree that a simple flush and refill can easily be done with just one can. My point was I guess not to skimp on fluid and try to " stretch " it.
 

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There was a thread here lately about a guy that was having the devil of a time getting his brakes bled and had used a whole can of fluid wiith no results. I find that a whole can just begins to get the system flushed out of air and it takes two cans to get the job done.
For real? I only use like 3/4 of a bottle of Motul 600 when I drain and refresh my brakes. Never had a problem with needing to re-bleed and brake lever is rock hard after zip tieing overnight. Anyone use that much fluid?
Sometimes I can get it done with just 3/4ths of a can as well. Especially if it is just a drain and refresh deal, and I do get a rock hard lever as well. But, there are those times when it takes a lot of fluid to replace what you have drained like when you completely rebuild the whole system.. I believe that since he was talking about doing the whole deal, ie pistons out, lines off full drain etc, that it wouldn't be all that unusual to use a whole can and a bit of a second. Maybe I should have said that I use just a bit of the second can. But, I'll agree that a simple flush and refill can easily be done with just one can. My point was I guess not to skimp on fluid and try to " stretch " it.
I'll keep that in mind when I refresh my calipers...it would suck to refresh them only to be short on fluid when replenishing the fluid.
 

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There was a thread here lately about a guy that was having the devil of a time getting his brakes bled and had used a whole can of fluid wiith no results. I find that a whole can just begins to get the system flushed out of air and it takes two cans to get the job done.
For real? I only use like 3/4 of a bottle of Motul 600 when I drain and refresh my brakes. Never had a problem with needing to re-bleed and brake lever is rock hard after zip tieing overnight. Anyone use that much fluid?
Yep that was // uhh is me. Wizo and lean were right I had air in my MC and there were hidden ones that were taped out. I'm still not done yet.
taking apart the calipers was easy but the bleeding has been a pain.
 

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Discussion Starter · #13 ·
Found the problem. The fork seal was leaking bad enough to run down the fork and into the caliper and gum it up.

Forks are off and will be sent to Mike at GMD this week. They were due for a fluid change anyway.
 

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Thanks guys. The problem seems to be that one of the pistons is stuck (won't push back). Perhaps I'll keep my eyes open for a used caliper or calipers, swap them and then try the rebuild so I'm not fucked if I can't get it right.

Anyone got a set of 4 pots lying around?
Crap usually gets trapped ahead of the seal, and hardens, somewhat, to the point that the pot doesn't want to move back.

Keep in mind that the pot is only moving forward/back a small amount.

Gotaa pull the caliper apart.....Get a set of fresh seals....clean the whole mess with brake fluid....not brake cleaner.....leave stored, if you need to store them temporarily, in a brake fluid wet rag, in a tupperware container.....

The main thing is to kee th seals wet until the whole mess is reassembled, otherwise they will dry out very quickly, and youy'll be doing the job over again.

BTW, I re and re the calipers on all of my bikes every spring.....seals are cheap, compared to missing a round or two for a brake problem. A set of seals here are about CDN$40
 

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yes I will... make sure you don't think "the fucking service manual's wrong" when you spend 1/2 hour looking at the seals and can't see the bevel that the service manual shows. They ARE uni-directional!


The manual makes it look like there's this huge, obvious bevel on 'em. There's not. It's hard as hell to see. But it's there. learn from my idiocy. I thought it was a misprint.

Oh - and as far as pushing the pistons out... it makes life alot easier if you try to extend the pistons as far out as they'll go (without completely popping out) before removing the brake lines. I usually pull the one caliper off the forks (leave the other mounted for now), remove the pads, and then pump the brake lever to extend the pistons out close to as far as they'll go without completely popping out. You have to use your fingers to hold the ones that want to come out easiest so that the 'hard budgers' will extend. When each piston is out about the same amount, and close but not at the point where they'll pop out, I stick a piece of wood or a single pad in between them to keep them from extending any further, pull off the other caliper, and do the same. Then remove the brake lines, drain the fluid, and pull the blocks out. If you do it right, they'll be loose enough to pull right out of the bores without the use of any air pressure.

The bevel is built into the caliper body, not the seal itself. If you just look at the seal after you put the new one in the body, you'll see it.
 

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Found the problem. The fork seal was leaking bad enough to run down the fork and into the caliper and gum it up.

Forks are off and will be sent to Mike at GMD this week. They were due for a fluid change anyway.
dude that fork seal was leaking since VIR and you just sent it in now?????
 
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