DOHC post=845998
The caliper piston seal was leaking. There was crusty dried brake fluid eating the paint on the bottom of the caliper. Maybe the brake fluid swelled the pad material and gummed it up?
Z1 calipers are notorious for that. The design of the piston seal and it's groove in the caliper tends to allow
very slow weeping of brake fluid (vapor?) behind the seal, between the piston seal and the caliper. We're talking many months. Pretty much every seal groove in Z1 calipers we see shows some damage from water-contaminated brake fluid (vapor?) weeping past.
When the handheld vacuum pump we use for brake maintenance began getting cantankerous & not holding vacuum, slmjim disassembled it. What was found was the same greenish corrosion on the aluminum piston and the aluminum bore of the pump body we often see on aluminum brake parts. Cleaning, a light hone of the bore and a little silicone grease restored the pump to full operation. Pump cleaning & maintenance has become part of our spring cleaning shop routine now.
We always used the external vacuum catch container to capture used brake fluid. Brake fluid has never entered the pump, only vapor. Our best guess is, that brake fluid vapors entering the pump bore was enough to cause the corrosion over the course of many years.
We've been able to salvage many OEM pads by sanding around the edges. The floating carriers can almost always be salvaged by gentle scraping around the edges with a dull-ish edge where the pad floats, then light sanding or vapor blasting. The corrosion expanding at the carrier edges seems to be what freezes the pad in place.
The used pad in the pic isn't in very bad condition at all. It can likely be salvaged unless soaked with oil from leaking fork seals.. Note that the thin shim, PN# 43076-001 is still in place on the inside of the pad located by the two shallow studs. It appears undamaged. That's an 'anti-squeal' widget. Don't ask us how or why it works; it just does, and should be transferred to a new pad when necessary. We also coat the pad side of the shim with a thin coat of disk pad anti-squeal potion when we assemble.
In order to help slow the passage of brake fluid vapor between the seal and caliper groove, we use a very small, fine, stainless-wire wheel in a Dremel-type tool to remove as much corrosion as possible by polishing. We then coat the inside of the groove with Bendix white brake grease using a Q-tip. It's a very stiff, almost solid white grease intended for brake parts that won't migrate oil out the way typical petroleum-based grease will. Onto brake pads, for instance.
For us, yearly brake fluid flushes on the Z1's have become the norm, to remove fluid that has become contaminated with water from
sorption. We flush even if the bike hasn't been ridden the past year.
There are two tiny O-rings on each caliper bolt. When reassembling the caliper, put the bolts through the outer caliper
first, slide the dust seals into place
, then roll the tiny O-rings into their grooves on the bolts. If the bolts are forced into the caliper holes with the O-rings in place, it's likely the O-rings will be damaged.
Good Ridin'
slmjim & Z1BEBE
