Topic: caliper rebuild

[Burnboy]

I'm in the middle of a rebuild on my gl1000 front end. I think ive scraped all the gunk out of the groove for the caliper piston seal. But once I put the seal in I cant get the piston in. Ive read that with the new seal in the piston should slide right in and be loose enough to fall out, is this true? Should I lube the o ring?

[goon 1492]

I have heard something about using some of the caliper grease just on the piston alone for installation, but wait for another opinon. I also reccomended just using a bit of brake fluid as a lube before but was wrong there also...

[Toxic]

since I am about to do the same, I'll sign up to hear what the informed have to say

[BeSeeingYou]

I just rebuilt the brakes on my 76F1.  You should be able to push them in by hand but it will take a bit of effort.  None of mine just dropped in or were lose enough to fall out.  A small c clamp also works for pushing them back in.  My new brakes work great with no hanging up or rubbing on the disc.

If you ever have to rebuild the back brakes here is how I did mine (the GL and F1 rear is very similar).  There is not enough clearance to get both pistons out at the same time so use a small long reach c clamp to hold one piston down while you use the master cylinder to force the other out.  Pop in the new seal, do a quick system bleed(it does not have to be perfect) and then clamp that one down and repeat the process.

[Burnboy]

thanks srust. I got the piston out with some persuasion from some compressed air, just cant get it in without forcing it, would hate to get it stuck again, maybe ill just keep scraping and hoping itll fit

[turkey4me]

I am no expert for sure, but been there.  Here is a link that could help

http://oldmanhonda.com/MC/Rbrakes.html

I have also read here somewhere that using aluminum foil works good to clean the seal grove without damage.

[Derby City]

I just did this chore this past Saturday (for the first time). When I put the put the piston back in, it was a tight fit.  I had to blow into the brake line hole to get it to pop out a little, then wrestled it out with my fingers (I would recommend compressed air, brake parts cleaner tastes like sh!t).  The piston definitely would not fall out just with the force of gravity. Also, I lubed the O-ring with anti-sieze lubricant.

My caliper also required lightly sanding some rust off of where the disc fit into the caliper.  When I was done with this, the disk would slowly fall out with just the force of gravity when I turned it over. I also put anti-sieze here too.

Post repair report:  So far, it's fully functioning with no leaks, squeaks or binding. I rode it around for a little while yesterday. Before the repair, when put the brake on, the brake would continue to drag after I let off the lever.
 

[TwoTired]

The piston should fall out/plop in when there is NO seal in the caliper bore.  The seal should definitely have enough friction to hold the piston in place with gravity being the only force applied to it.

There is a caliper rebuild walk-through in the FAQ. (For SOHC4, of course)

[Don R]

I use a little brake fluid to lube the seal

[Burnboy]

should it be loose enough that I would be able to push the piston in by hand?

[BeSeeingYou]

should it be loose enough that I would be able to push the piston in by hand?

It may be but it will require a bit of force.  The c clamp makes it easier.  It is a common way to do it on cars for the DIY'er.

[tlbranth]

I have a bottle of 'Hydraulic brake cylinder assembly fluid' that's made the job easier for me for years. It's compatible with all brake materials and fluids. When I assembled my K0 caliper, it went together very easily and the brake works great. Don't remember where I bought it but I've used it on cars & bikes and it's made assembly much easier. The small bottle I have will last a lifetime. I'll bet NAPA sells it.

[Burnboy]

Napa and Fastenall are my 2 new favorite stores.
 

I have a bottle of 'Hydraulic brake cylinder assembly fluid' that's made the job easier for me for years. It's compatible with all brake materials and fluids. When I assembled my K0 caliper, it went together very easily and the brake works great. Don't remember where I bought it but I've used it on cars & bikes and it's made assembly much easier. The small bottle I have will last a lifetime. I'll bet NAPA sells it.