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Discussion Starter · #1 ·
I am not experienced in working on or repairing disc brakes. After removing the calipers from my GL500 and removing the pads, the pistons look really badly rusted to me (will try to attach picture). It would take a lot of sanding / polishing on these to make them smooth as new. This one has already been cleaned up a lot - it was totally covered in rust and black crud.

Are the pistons available and where? Looking at the fiches, they appear to be quite expensive (if available), and given the condition of these, I expect all the parts and seals behind them need replacing too. What is the best course of action here?

Are there packaged rebuild kits, or does one need to individually source the required parts?

Find a complete replacement pair of calipers?

I also plan to replace or rebuild the MC and replace the brake lines with SS.





 

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I am not experienced in working on or repairing disc brakes. After removing the calipers from my GL500 and removing the pads, the pistons look really badly rusted to me (will try to attach picture). It would take a lot of sanding / polishing on these to make them smooth as new. This one has already been cleaned up a lot - it was totally covered in rust and black crud.

Are the pistons available and where? Looking at the fiches, they appear to be quite expensive (if available), and given the condition of these, I expect all the parts and seals behind them need replacing too. What is the best course of action here?

Are there packaged rebuild kits, or does one need to individually source the required parts?

Find a complete replacement pair of calipers?

I also plan to replace or rebuild the MC and replace the brake lines with SS.





Try to remove the pistons from the caliper. I've used vise grips applied to the lip of the piston covered with a cloth. Gentle twisting/pulling usually gets them out. It is the condition of the pistons below the square O-rings that is most important. Surface rust above the dust seals may be removed with a rust removing solvent followed by light sanding with a very fine abrasive paper. You may discover the calipers are too far gone to renew. These parts come up on eBay quite often.
 

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I wouldn't use anything to grab the piston if you plan on reusing it. I'm assuming the caliper wasn't seized, use a rubber tipped blow gun in the line hole to blow the piston out. This can be messy and it will really shoot out so brace yourself. You can also use the M/C to push it out by attaching the line, bleeding it, and slowly squeeze it out.
 

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I got mine from Old Bike Barn. Don't use them if you plan on riding anytime soon. I think it was around $30 for the piston alone.
 

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And another thing! I bought a blue point brake cyl hone from snap-on that you chuck into a drill for this, used once put into the junk drawer of my tool box. Well i came across it today and one of the stones fell off
 

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If the corrosion is only as in the picture and not actually the part that enters the cylinder you may be fine.The area inside the cylinder is the part that counts.That must be corrosion and score free.Do the pistons leak?
 

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Wrap the calliper in a rag if you're going to use compressed air to blow the pistons out.



Or, if using compressed air put a G clamp on each piston. Then you can "walk" them each out a bit at a time. This saves one coming out before the other has moved, as if one piston comes out first the air line will no longer work to remove the other. The same applies to M.C. hydraulic pressure too.
 

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The corrosion on those pistons is just a little bit too far gone for my liking.

If you ever install new,thicker pads the pistons will have to retract back into the caliper to a point where the corrosion on the piston will come into contact with the dust seal and/or piston seal with possible damage to them - it already looks like you have a `dust seal hernia` going on, can i see it squeezing out of the caliper body?

New pistons are available, but kinda` expensive, at least over here.

Add on seals etc....

Maybe a used caliper off one of the many 80`s Honda`s that used those particular twinpot calipers would be a better bet?
 

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Discussion Starter · #9 ·
Eurovee - I lack experience here, but my gut was telling me the same thing you say about these.

Yes, the dust seals are squeezing out a bit. These pistons are stuck hard, but I will go ahead and see if I can get them out.

Even if this just becomes a destructive "dissection" it will be educational for me.

I may have to just find complete replacements. Does anyone have a list of which bikes used the same caliper? It's a GL500I so has 2 of them - both are in similar condition.

Thanks to all who took time to reply.

If I get them apart, I will post pictures of the disassembled parts.
 

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Georgefix and TAS do the pistons.

A quick search on ebay found dozens of suitable calipers listed of varying condition and prices.

Try searching for these models and see if they match up;

1981 CB400 T C400T



1981 CM400 CUSTOM CM400C



1986-87 CMX450 C REBEL CMX450C



1986 CB450 SC NIGHTHAWK CB450SC



1982 CX500 C CUSTOM CX500C



1982 CX500T TURBO



82-83 FT500 ASCOT



89-90 GB500



81-82 GL500 SILVERWING



84-86 VF500 F INTERCEPTOR VF500F



83-85 CB650SC NIGHTHAWK



84-87 VF700 C MAGNA VF700C



84-85 VF700 S SABRE VF700F



1982 CB750 C CUSTOM CB750C



82-83 CB750 SC NIGHTHAWK



81-82 CB750F SUPER SPORT



1982 CB750K UP TO FRAME CM30151 (NISSIN)



1988 VF750C MAGNA



82-83 VF750 C V45 MAGNA



82-83 VF750S SABRE



1988 VT800 C SHADOW VT800C



1982 CB900 C CUSTOM CB900C



81-82 CB900F SUPER SPORT



1982 CB1000 C CUSTOM CB1000C



81-82 CBX



1983 CB1100F SUPER SPORT



1982 GL1100 GOLDWING



1982 ASPENCADE GL1100A



1982 INTERSTATE GL1100I



85-90 VT1100 C SHADOW 1100 VT1100C



92-93 VT1100 C SHADOW 1100



1982 CX500TC TURBO



84-86 VF500 F INTERCEPTOR VF500F



1983 CX650T TURBO



1982 CB900 C CUSTOM



1983 CB1000 C CUSTOM



1982 GL1100 GOLDWING



1982 GL1100 GOLDWING ASPENCADE GL1100A



1982 GL1100 INTERSTATE



83-86 VF1100C V65 MAGNA VF1100



84-85 VF1100S V65 SABRE







Look for VF500/750/1000, CB750/900, CBX, etc.

The design is slightly different on some models but it`s essentially the same caliper.



Those pistons will pump out if you hook them back up to the master cylinder.

I suspect the pistons will be in OK condition where they have not been exposed, it`s just the rust on the exterior part that may cause problems when they`re pushed back into the caliper when new pads are fitted.

Hmmmm.....
 

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On a related note, see this thread on the old forum.



The pistons are Honda part number 45107-ma3-006. An aftermarket replacement is also available, K&L part number 32-1176. They sometimes show up on ebay, but also try a google search for "K&L 32-1176". You may be pleasantly surprised.
 

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I bought a gl500 that sat 13 years and the calipers looked just like this. I used my air compressor to pump the piston out via the bleeder hole. Very exciting when the first one "pops" out. (Sounds like a shot gun blast}Then I put the piston back in with a C-clamp to hold it and more compressed air to blow the 2nd piston out. Next remove the c-clamp from the first piston and pull it out with vice grips. Wrap the whole rig in a heavy towel or blanket so the pistons don't fly out and hurt you or something in the garage. I've not bought new pistons yet but all the rest of the system looks good and usable.
 

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Discussion Starter · #13 ·
Just a quick update on this that might help anyone else with calipers in the same condition. These calipers were off the bike and the MC is also in dire need of a rebuild, so could not try pumping them out with the MC. I tried 100 psi air, but could only get one of the 4 to pop out (BANG!) - the others would not budge. I finally resorted to using a grease gun attached to the bleeder (you need to partially back out the bleeder of course, and use one of the caliper mouting bolts in the banjo bolt hole to seal it up). I was a bit apprehensive about this technique as I thought it would make quite a mess to clean up. And it does - but it works fine with almost no drama, like using air does. It is a very controlled process. Scoop the bulk of the grease out of the piston pockets with a small thin flat piece of wood. This will be the largest volume of grease in there by far. Getting all the grease out of the fluid passageways is a bit of a pain - use compressed air first, then some degreaser, then lots of brake cleaning fluid - use a fresh can with lots of pressure. This will not dissolve the grease - you have to flush it out by displacing it. Then I boiled them in the ultrasonic cleaner for an hour or so. Then used a dental pick and Dremel tool and compressed air to get all the calcified gunk remaining out of the seal grooves.

They are now ready for rebuild. The pistons are too far gone for my comfort, so will bite the bullet and get all new parts for them. The parts cost counts up fast for the twin caliper setup, but I do like to be able to stop reliably when I need to.

Next will be the MC and new brake lines.

I got this bike to learn to wrench, and am getting my money's worth and then some.

Lots of fun.

Lucky I picked a GL for this process - this and Shep's forum are absolutely the best of their kind for repair info!!
 

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Glad you are getting somewhere.These are good bikes to work on and you are just coming up against what a lot of us have e.g neglect and lack of regular servicing.Many of the bikes were dumped and left for years of course there's decay to sort out.

Here's in the UK many of the bikes have been run to high mileage and again abused by neglected regular servicing.Brought back to good condition there's no reason they won't give tens of thousands of miles of pleasurable riding.

Whilst you are waiting for parts strip and service the Starter motor.It's pays big dividends,



http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=8&t=208
 

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Discussion Starter · #15 ·
When it comes to the CX/GL brake calipers, there seems to be a lot of discussion about pitted and stuck pistons, but not much said about the slider pins. The pin on one of my calipers was stiff but could be moved by hand. It was disassembled and the little bit of remaining grease was very stiff, so then cleaned, regreased, and reassembled with new boots - one done, one to go.

The slider on the second caliper was immoveable by hand, even though the boots looked to be in great condition on both ends (first picture). I had to drive the pin out with a bolt and hammer to get it to move. The reason can be seen in the second and third pictures. Even after jigging it up so I could sand it with strips of sandpaper, the pin is badly pitted (last picture)and will be replaced (hope there is a good source for these).

Moral of the story - make sure these slider pins are taken apart and checked closely even if they look good, and even if they move freely.

Putting the pin back in and getting the boots in place is a bit of a pain, but not doing this could make the rest of the rebuild useless. I'm doing both calipers with all new pistons, seals, pads and boots. BTW, has anyone used the grease pictured here? It says it is suitable for use on brake calipers and for contact with rubber components. It's expensive, but this little bottle is probably a lifetime supply for everyone on this forum.

Tom









 

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Nothing worse than a slider pin that won't, it'll ruin one of your pads in no time.
 
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