Rebuilding brake caliper

I'm wondering how difficult it is to rebuild the front brake caliper on a 82 XJ550 Seca. The Clymer manual says it's best left to a pro but I see rebuild kits on ebay that look pretty inexpensive and basic. Is it a big deal? It's pretty cold here so I won't be riding for a bit. Sounds like an easy project.

 

piece of cake. it will take you maybe a couple of hours, tops.

get a new o-ring kit.
remove caliper from the fork, leave the banjo fitting attached for now.
remove piston from caliper -- this may be tricky if it's stuck. some people swear by using compressed air, but IMHO that can be dangerous. If the brake system still has some life left in it, just keep squeezing the brake and topping off the reservoir as the piston slowly inches out.... If that does not work, disconnect the brake line and cap off the banjo bolt hole with a solid bolt (10mmx1.25 if I remember correctly). Get a grease gun and attach it to the bleeder valve. loosen the bleeder valve and pump the caliper full of grease. That piston WILL come out.

Thoroughly clean out the grease, gently scrape out any residue from old brake fluid. Pry out the old rubber seals. Scrape the gunk from the seal grooves (important!). Once you got the caliper body cleaned out, install the new o-rings.

The piston itself might need some TLC as well... I prefer a buffing wheel with some black rouge to shine it back up and remove any corrosion. A dremel with a polishing attachment will also work. Do what you have to do to make the piston shiny, smooth and free of burrs (a metal file will work for those).

Wet the piston and the rubber seals with some fresh brake fluid, and gently press the piston back in. Make sure it goes back in straight.

Now it's ready to go back on the bike.

EDIT:

Forgot to mention something... Keep track of all the pad shims (they're reusable) and make a note to self how the retainer spring goes back in behind the pads.

also, the pin on which the caliper moves... take it out and clean it real good, and re-coat it with some silicon grease (don't use petroleum grease).


I'm sure I forgot something, but someone else will chime in shortly...

 

What about honing out the caliper? Is this not done on these calipers when rebuilding?

 

Stereomind has given a pretty good run down for you. I cleaned up my brake a couple years ago. The piston came out by working the brake lever and pumping the piston out. I put the whole caliper inside a plastic bag to contain all the fluid. No clean up that way. There was some rust on the piston that came off by just scrapping with my thumbnail.
This is one of the easiest things to do on the bike and should make a big difference. Putting new pads on I hope.

 

On this type of caliper, the piston only makes contact with the rubber o-rings, so you don't have to worry about honing.

 

Thank you Stereomind and RangerG.

Sounds pretty simple. I actually put new pads on already and had a tough time getting the piston to retract. The whole caliper doesn't move on the slider as freely as I would like either. I was too impatient at the time to do a rebuild but could tell it would be a good idea. I guess now's the time!

 

They don't make contact in most car calipers either, but honing is normally part of the rebuild operation there. It's not about scratches from piston contact, but about scratches from particles that have become embedded in the seal, and from pitting due to contaminants in the fluid. If the caliper wall isn't smooth, you're not going to get a good seal, and, at best, you're going to reduce the working life of the seal.

 

Honing is not a bad idea on brake calipers, and SQL is correct in his analogy. Remember, honing is NOT an attempt to "remove material", but rather it smoothes any surface imperfections down to a base level.

One other issue that comes up with these calipers is the build-up of rubberized "gunk" inside the fluid and dust seal recesses.....this material MUST be cleaned out fully (and it's kinda difficult to do). A wire brush attachment on a dremel tool is one good way to (patiently) accomplish this. You can try soaking the caliper ovenight in carb dip to loosen up such material before attempting to whirl it away.

 

So how does one perform the honing? Is this a DIY or a trip to the shop? I'm assuming it's similar to brake rotor cutting (which of course is done with specialized equipment) except more of a "polishing".

 

It's normally done with a hone stone setup that fits into a power drill.

Most auto parts stores stock them. At Autozone it's listed for about $17, for instance.

If you have an old caliper to practice on, it might be a good thing.

 

First take it apart and look. The most common problem with the front caliper on those bikes is the "sliding pin" that gets all rusted in place and becomes the "beat it with a big hammer" pin. Both my 550 Secas had the issue. That's the pin that the sliding portion of the caliper hangs from in the fixed portion, not the pin that retains the brake pads.
Honing the caliper is not difficult but it also isn't necessary about half the time. Only a careful inspection will tell you though.