Caliper disassembly and seals

[Burque73]

I decided to open up the calipers on my '83 GS850G and inspect/ clean them up. I had never attempted this before so I really took my time going through them.

The front went very smoothly. The manual said to use compressed air to pop the piston out, but that wasn't happening. As mentioned in the tutorial on Basscliff's site, a couple of pry things worked just fine. using one on each side of the pistons (couldn't take pics and hold two levers). I has some scrap wood paneling that I could stack up to get better leverage as needed. A very fiddly process, but effective.



No wonder they were sticking. Look at the jelly underneath! In all, the pistons are in real good shape though.



I guess I over torqued the bleed nipples a few years ago when I bled the system. Maybe the bit of brake fluid on the threads made it easy to over do it or some corrosion formed making them stick, in any case I certainly didn't want to chance breaking anything. I used a torch carefully heating up the end of the nipple and worked them back and forth in between shots of WD-40. They gave up without snapping. Yay!

The WD-40 really loosened up the crud on the rubber bits and the calipers too. I still scrubbed quite a bit, followed by blasting all the tiny holes out with compressed air. Everything cleaned up nicely so I decided to reuse the seals and boots. I went over the pistons with some 1500 grit sandpaper too.



Back together now. Looking and operating much better.



The rear caliper did not go as smoothly more to follow.

[Burque73]

Getting to the rear caliper now.

This pic was from three years ago when I installed the steel lines. My brake line was a bit too long so it had to loop back to the caliper. Anyway, after removing the caliper I wanted to use the brake pedal and pump the pistons out a bit before disconnecting the lines, but the darn loop made this impossible. I went ahead and pulled everything apart and fiddled with the wood spacers/ pry things again. It worked, but a bit more challenging this time.



I couldn't separate the two halves of the caliper. Heat, oil, impact no dice! I figured I'd just do the best I could without splitting them. I managed to get the pistons out but one was really stuck. In all, they're in pretty good shape so it must have just been the build up of crud holding them in.

The seals were tricky to get out without poking them with a paper clip or something. I sanded the end of a plastic stick to a point and with a bit of WD-40, wiggled it loose.



I sprayed everything with WD-40 and let it soak overnight. In the morning, the crud was still hard though. Brake fluid seemed to loosen it up, so I dropped the small bits into a bowl of brake fluid to soak for a few. Well, a friend called and I had to leave for a few hours. When I got back to work, the crud was definitely loosened, but the rubber boots were too flexible. They felt more like latex than EPDM (or whatever Suzuki used.)

I proceeded to shine up the pistons and reassemble in the same manner as the front. Unfortunately, the seals had been stuck for so long that they distorted like a windshield wiper held in the same position all the time. The boots are probably useless too. I'd compare them to three day old socks that are all stretched and don't fit right anymore. I'm not sure if the fluid bath softened them up or they're just shot from age, but I'll order new ones.

After farting around with these things for hours, my work area was a disaster. Not that it was super clean to start with though...



Any suggestions on separating the two halves would be welcomed, or if that's even necessary at this point. Also, if someone could speak to how brake fluid could damage the rubber or not that may help.

Thanks guys.

[Gorminrider]

Those look very nice, now! Brake fluid won't hurt any rubber that's around the brakes. OTHER types of grease and solvents may...Stick to a correct "brake grease" for anything (judiciously) greased. I've been doing all my bikes with a silicone type. "Brake safe" tubs o' axle grease seem to go gummy-sticky especially in my particular calipers on the 400s and 650-the front brake caliper slide-pins...where there's a vacuum and where one side has a strange rubber sleeve....

Not sure what you mean per "separating the halves". I don't recall ever wanting to do such a thing! if your piston holes are good and passages clean, that's all there is, isn't it?

[Burque73]

There is a passage between the two halves I couldn't really get to. I blew brake cleaner and compressed air through so that's probably good enough I suppose.

The two halves are held together by the socket head bolts, #6 below. The manual shows opening the halves and cleaning/ inspecting everything. As far as grease, I used Sil-Glyde silicone grease where applicable.

[Gorminrider]

ah,so. I guess the two halves might make the dual pistons easy to get back in..but if you can avoid it...well, I would, unless you really can't get them in without taking them apart, for what that's worth to you....

[Sandy]

No big deal to split the 2 halves. Just metal to metal contact and 1 oring for the fluid passage. Would make it a whole lot easier getting the pistons and seals back in.

[Grimly]

No big deal to split the 2 halves. Just metal to metal contact and 1 oring for the fluid passage. Would make it a whole lot easier getting the pistons and seals back in.

Especially the rubber boot seal on both halves. It's a total pig to get back in place when the caliper is un-split.

[Burque73]

I'll find out today if the pistons and boots will go back in without separating the two halves. Fingers crossed!

Check out the difference between the new and old boots.

The old measures about 2-1/8" OD and feels noticeably softer than the new.




The new one measures about 1-7/8" OD.



They're a full quarter inch different in size! I'm still not sure how they even fit before. All I can figure is soaking in brake fluid changed the composition of the rubber.

[dorkburger]

As Sandy noted, its generally not a big deal to split the halves..... if the bollts cooperate.
I was pleasantly surprised to find mine pretty clean when I did them a few years ago. No parts needed, just a cleanup. No built up gunk either despite the bike sitting form 1986 to 1999 when I bought it. I did change the fluid when I got it, then every few years thereafter.

I should do the rear brake one of these years....


http://Untitled by Glen Brenner, on Flickr

[Gorminrider]

If it gets to "tucking the seal" rather than the "jeweller's screwdriver that can be too handy and pierce a seal,(ie rotating its lip to fit the groove etc.... popsicle sticks can be handy they are not awful strong though. Other less-destructive tools I would try are guitar picks and similar tools plastic tools used to take smart-phones apart...I have a vague memory of cleaning my 650s rear disk and I think you should be able to get the seal in starting at the difficult less-room" side. I know I didn't split the halves.

[Burque73]

Wow, Glen. I'm surprised it sat for that long and still looked good inside, especially with the humidity up there.

The bolts holding the halves together may as well have been welded on. Impact, torch, penetrating oil all have had no results. If I can avoid splitting them, and sounds like I can, that's the plan. I may save some broken parts trying to force things and wind up shopping for more parts.

Thanks a bunch, Gormin, for the popsicle stick and guitar pick ideas.

[bwringer]

You need a stout air impact to shock those bolts out and separate the halves. I've never had any luck with just grunting them out.

Harbor Freight has a fantastic set of impact hex bits.
https://www.harborfreight.com/12-in-...-pc-67895.html
Made in Taiwan and very high quality.

If all else fails, you could drill the heads off the bolts.

There's a little flat seal in there that it would be good to replace, and obviously it's going to be vastly easier to complete the rebuild if you're not trying to build a ship in a bottle.

All that said, if you really can get it properly clean and reassemble without splitting the caliper, then you should be fine. I'm not sure that's going to be possible, but it's worth a shot if you're not in a hurry.

[Burque73]

Thanks, Brian. I actually got the pistons back in and with a litle help from a plastic stick, the seals popped right into place. The caliper is back on the bike, bled and ready to go.

[bwringer]

Thanks, Brian. I actually got the pistons back in and with a litle help from a plastic stick, the seals popped right into place. The caliper is back on the bike, bled and ready to go.

Excellent!

Good to know that's possible. Certainly not easy, but possible.

I shall dub thee "Roger the Steely-Eyed and Nimble-Fingered".

[Guest]

I rebuilt the rear and one front caliper yesterday and have the other front to do today. I split the halves on the rear and used compressed air to pop out the pistons without a hitch. Just wanted to add I used k&l rebuild kits and can see inferiority compared to oem. I would go with oem if to do over....which I may in a year or so of use. Most unimpressed with the caliper bolt boots for the front calipers.