Rear Caliper Rebuild

[WhiteBeard]

Hey guys,

I changed the brake pads on my bike today, or the rear brake pads to be more precise, since I never had the time to put the front ones in.
The pistons were frozen, no chance of pushing them in. I tried to force them in using a screwdriver or locking pliers, but I only managed to mess up the front of the calipers (I'll come back to that in a moment).

So I removed the caliper, opened the caliper up and put it in a vice to push the pistons back in place. It worked!

Cleaned the two halves with brake cleaner, bolted them back together, put it back on the bike, inserted brake pads, put new brake fluid in there and bled the brake system.

However, now it seems to be leaking fluid from the rear end of the caliper each time i press the brake pedal down. I figured it might be the small o-rings that fit in between the two halves, so I redid the whole procedure and took a look at the o-rings. They did look a bit rugged, but since I didn't have any replacements, I tried to refit them to make a better seal, than bolted them pack on again. No luck, the brake is still leaking (not much though).

I took a look at RPM's brake caliper rebuild kits, but they didn't seem to contain these o-rings (and they are not represented on any parts microfiches I have looked at). I'll go to the Yamaha shop and see if they can order them for me.

Also, I did manage to mess up the shiny outside of the caliper to quite some extent through my use of locking pliers.
Is it possible to buy replacements for the round silvery part of the brake caliper?



Or is it better to go ahead and look for a new caliper?

Do you guys usually keep the rear caliper OEM, or are there other options? As far as I know, I have the original size rear wheel. The bike is a 1985.

The good news is that I rarely use the rear brake, so I can still ride the bike while ordering the replacement parts.

[FJ111200]

You can get the o rings but don't ask me where, someone was on about it the other week.  I usually push the pistons in with locking pliers like you did. Sshh, bit of an animal on the quiet.
If you go down the route of finding another caliper, you can use a front one from the opposite side if a rear is hard to find, that is a left front.
Only drawback is that it will have only one bleed nipple, but jeez will it stop your back wheel turning to the point of locking up.

[FJmonkey]

You can take your knackered O-Ring to some hardware stores and other specialty shops and they will size it and sell you a fresh one. I have a working rear caliper I took off when I did my GSXR rear wheel and went under-slung using the GSXR caliper. If you run out of options I could take my old caliper apart and size the O-Ring for ya. I have a few shops around that stock O-rings so finding them is easy.

[FeralRdr]

I had this same issue last summer when I rebuilt my brake calipers.  I was able to reuse my old seals, but before I decided to attempt reusing them, I contacted Randy (RPM Racing), and he advised me:

I finally got a caliper apart yesterday and that is a square cut sealing ring. I would not hesitate to replace it with a Viton o-ring. I would take the caliper down to a NAPA store and select an oring that will fit on the shoulder but is not much thicker than the recess in the caliper body.

It doesn't take much compression for it to seal.

Randy

Hope the info helps.

[fj11.5]

I have about 3 calipers not being used, you can have the best one for the cost of postage, but you may find one cheaper state side

[craigo]

I have a spare OEM caliper off a 90 3CV if you want. Just pay postage from Lakeside, CA 92040

CraigO

[Pat Conlon]

Kudos Craig

[craigo]

Thanks Pat,

And I'll throw in the SS line and sintered pads as well.  

CraigO

[WhiteBeard]

Wow.

CraigO, thank you so much for your offer, I have PM:ed you.

And thank you fj11.5. If all my options run out, I will get in touch.

I have to say, I'm kind of overwhelmed. Seriously.

[craigo]

No problem Nat,

Anyone know of any issues putting a 90 rear brake on a 87?

I am just going to send the whole assembly to you including brake arm and carrier. The axel is the same, I know. But I am not sure of the mounting points from the different years.

PM me when your ready and I'll get this boxed and ready to ship.

CraigO

[WhiteBeard]

Actually my bike is an 85... 

So does anybody know if I would have a problem fitting a 90 rear brake on an 85?

[craigo]

Nat,

Post or send me a better pic of your brake/swingarm assy. It looks like they are the same on the 85 and the 90, just different color paint. Mine is gold and made by Sumitomo. However, I am going to send you the whole assembly from my 90. I know that the axles are the same so the carrier I have will mount up to your axle. Just not sure of the spacing.

C'mon someone in the know, chip in here.

CraigO

[WhiteBeard]

This is the best one I have stored on the computer.
If you guys need a better photo, I'll just grab my camera and go out and take some new ones.

[FJmonkey]

Nat,
Post or send me a better pic of your brake/swingarm assy. It looks like they are the same on the 85 and the 90, just different color paint. Mine is gold and made by Sumitomo. However, I am going to send you the whole assembly from my 90. I know that the axles are the same so the carrier I have will mount up to your axle. Just not sure of the spacing.
C'mon someone in the know, chip in here.
CraigO

Option 2 would be use my 86' rear caliper.
Yamaha part number for 85' caliper 4BH-2580W-01-00
Yamaha part number for 86' caliper 1FW-25810-50-00
Yamaha part number for 90' caliper 3CV-2580W-01-00

Incidentally, the rear bracket and rotor are the same part number for 85, 86 and 90 years. I am thinking they look different but bolt on all the same.

[WhiteBeard]

Here are some more photos I found, taken last summer not too long after I bought it: