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Brake cylinders

1109 Views 9 Replies 6 Participants Last post by  JWink
Attached is a picture of one half of my GL650-#2 brake calipers. The front brakes were the most obvious thing wrong with the bike when I picked it up 2 weeks ago, and I'm wondering if this was a contributor. It appears to me, unencumbered by knowledge, that the back end of the cylinders have worn through to a mesh-like support area. Since I've never seen the inside of a Honda caliper, I'm not sure how normal this is. I don't know why there would be friction-type wearing there, but maybe after 70K miles that is what happens. All four cylinders have similar patterns. On a maybe-related note, one cylinder had the pile of goo seen in the other pic by the fluid holes in the back end. It has the consistency and color of moly grease.

The o-rings and pistons look OK, but the dust seals are just about kaput. Should I spend any more time cleaning and rebuilding these calipers?

(I got a "Can't use a .jpg image type" error when posting this. Has something changed? Took out the image code, so maybe someone can fix it.)
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You are looking at the normal casting marks at the bottom of the piston bores.
Well, that was easy. The cylinders are cleaning up pretty easily, although getting the o-ring groove spotless may requirre a power tool of some sort. I'm thinking a very small, soft-wire/stiff-bristle brush attachment on a low-speed Dremel may do the trick.
If you use the Dremel, don't overdo it. Try to use a brass brush and just make a quick turn or two around the circumference. You don't want to round the edges of the groove too much.

I wonder if the gunk you found is actually grease? I know of several references on the old site about how to get a grease gun on those Zerk fittings. Maybe a PO actually did it! If he would have opened the valve a little, you could certainly pump some in.
Some grease may have been pumped in--I guess that would be one way to force pistons out if other ways failed. No matter, it's gone and just a curiosity now.

I've got the grooves pretty clean, but I always think back to the Larry Motto: "If you are doing something, don't do it half a**ed". Once I get it back together, I really don't want to take it apart because a piece of something is keeping it from making a good seal. Got the concept though of doing no harm. Thanks.
Count me among the pretty naive, but I do know the diff between a grease hole and a bleed hole. When I return from Vegas -- not riding
-- on Friday I'll get everything back together and see if the binders work at high speed.

Thanks Blue for the birthday thoughts. What do you get a guy that has three motorcycles? A bigger garage!
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