rebuilding rear brake caliper

I"m having a new tire installed on my rear wheel and I'm installing new brake pads, so I thought it would be a good idea to rebuild the caliper while everything is off the bike. '04 no abs with 49,000 on odo and I'm sure this is the first time for rear brake caliper service. I have taken the caliper off and have separated it, and I'm trying the compressed air method suggested in shop manual for pushing the pistons out. I cannot get the two outer pistons to budge. I would appreciate some ideas on how to remove the caliper pistons.

Thanks

It's probably a little late to say this, but unless there's something specifically wrong with the caliper, there's no need to service it.

This is probably a dumb question, but is the circuit you're blowing into capped off at the end?

If they're truly stuck, they might be cocked. Insert a piece of dowel and give them a little jiggle to see if you can break them loose.

--Mark

Got the pistons out by applying some pressure on the interior walls and twisting a little. I already have the new seals, so I am going to proceed with the rebuild, should be very simple.
Next question: Once the system is re-installed, am I correct in assuming that I need to do an entire system bleed as pe manual?

Standing by the white courtesy phone ...:call:

sent an email Igofar

kendall said:

Next question: Once the system is re-installed, am I correct in assuming that I need to do an entire system bleed as pe manual?

Click to expand...

By now you probably have had this question answered - yes. The brake fluid should be changed every two years or so, anyhow. Brake fluid is hydroscopic - it absorbs water from the air - and this water does the inside of aluminum calipers no good. Years ago when I was rebuilding auto brakes (not necessarily calipers) I honed the cylinders before installing new rubber parts. More recently, I found pitting inside the calipers on my Guzzi - which forced me to buy new calipers.

I will post an update, excuse me if I get terminolgy wrong.

I had a phone conversation with Igofar last night about this project and I want to publicly thank him and extend kudos for his advice.

Last year I put new pads on both front brakes and took the time to completely drain and replace brake fluid and bleed the entire brake system per the service manual. I bought a compressor driven MightyVac to do the job. What prompted the fluid change and system bleed, besides it probably never having been done by previous owner, was the infamous clunking of the secondary control module indicating air in the system. It went well enough, but what a PITA!

This last week, it was time for a new tire and new pads on the rear so I thought I would give a go at rebuilding the rear caliper. RockyMountainATV stocked the seals and had them to me in one day. Initially, I had a tough time getting the caliper pistons out, only one would blow out with air and they were pretty gummed up. Applying some pressure to the inside walls of the pistons, then twisting and pulling and they reluctantly came out. The caliper rebuild from that point on was a no brainer per the manual.

Igofar gave me some great advice on the steel sleeve that runs on the needle bearings in the bottom bolt hole of the SCM, and warned me against damaging the fiber insert in the top SCM bolt hole. I'm surprised I didn't bung it up last year when I had it apart. This go around, I cleaned up that steel sleeve, and packed the needle bearing with grease prior to reinstall.
This time around on the bleeding of the proportioning valve on the right hand side of the bike, I took Igofar's advice and lifted the fuel tank to access the valve. Igofar must have long skinny fingers because just lifting the tank did not cut it for me, I still had to loosen the side plastic enough to pull it away from the bike about 1". Everything is complete and buttoned up. Igofar suggested I NOT use the MightyVac bleeding system, but since I am a one man show, spent $100+ on the danged thing, I went ahead and used it. I might in the future look into getting one of the Motion Pro or Tusk one way valve kits. There were some less than great reviews on the RockyMtnATV website so I hesitated making the purchase, plus I wouldn't have gotten the tool until Monday and I wanted to get the job done today.
Many thanks to all, for the excellent pictorial essays, tips, and how to's on this. I am not a wrench, but try to do what I can on the bike. With help from the members here I'm kind of surprising myself.