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Discussion Starter #1
go to ACE hardware store, and get a brass adapter my air hose end is 20"x20 tpi threads per inch. so get a female adapter say 1/2x20 ( your air hose end may be different. X 1/4 male end. and i ground off the threads and cone shaped the end so my (tap and die set 10mmX1.25 tpi. and the brass makes it easy to tap new threads. see picture. put the caliper in a vice and screw the air hose to the adapter-and the caliper.

i soaked the caliper with penatrating oil overnight. secure the air hose in case it popps off. start the compressor. my pistons both popped out about 60 psi.the rebuild kits on ebay are about 34.oo without new pistons. hope this helps.also you tube how to rebuild the caippers. they have some good tips.
 

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Yours must not have been stuck, I have put 120 psi on a lot of them that were and never have had a single one pop out. Always had to use hydraulic pressure on them. They will of course come right out if they don't need to be rebuilt.
 

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Discussion Starter #3
when installed the "O" rings i installed 2 new fat 'o' rings in the same caliper. anyone done this before. guess i'll have too de-do it. the first one is suppose to be a narrow one, but the fat one went in fine
 

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The pistons use squsre rings. O-rings will probably not permit release, and the brakes will drag. Double o-rings are always a bad idea. Using air to remove pistons, put a rag in the caliper to prevent damage when the piston pops and cover with another rag to help with brake fluid spray. If air won't do it or you want a more controlled process, plug the fluid line with a bolt and put a zerk fitting in the bleed position. Then pump the piston out with your grease gun. The caliper needs to be cleaned up anyway.
 

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Discussion Starter #5
the "o" rings came with the over haul kit. i simply use 2 wider "o" rings in the grooves instead of a narrow one in the first groove. the caliper is already cleaned up. i'll just take it apart again and install the narrow "O" ring today. thanks for the info.
 

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Discussion Starter #6
pulled the caliper. both pistons popped out at about 60 psi. installed the thin "o" rings in the first groove, and reinstalled the caliper.so now to bleed the brakes etc
 

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The exploded drawings on parts fiche show single square ring for seal and thinner ring for the dust seal. No o-rings are shown. O-rings have a round cross-section. Using a MightyVac to pull fluid into the calipers really sped filling and bleeding the front system on my '79 GL1000 last month.
 

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I know this is an old post but a lot of people do not realise how the seal works.
It is a sqare section seal but the groove it sits in is not square bottomed, the bottom is at an angle to the piston bore so that when the seal is fitted it turns into a diamond cross section.

This means only a corner of the seal is against the piston, if there is a big gap to the pad fluid will push the piston through the seal, which twists a small amount, untill the pad touches the disc.

Once the piston has to only move a fraction the seal twists as the brake is applied and it is only this twist in the seal that pulls the piston away from the pad.

Consequently the seal groove needs to be spotless and from years of experience i can assure you that water in brake fluid corrodes the groove and leaves behind some concrete like crap. So much so thay i have found you need to use a dental pick to dig it out as a dremel wire brush just polishes the crap andleaves it shiny but still there.

Hope this helps you understand how it all works and what to do to rebuild a caliper so it works for years.

Cheers

Bryan
 
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