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I'm restarting working on the bike to get ready for the spring. So almost there, only brakes checking and disambly missing before painting the caliper...
After disassembling the rear caliper fond this strange black marks inside, As I have never done this on a DYNA, is this looks fine to you or have you ever seen something similar?
It's the raw casting. When the bores were milled, the milling didn't go all the way to the bottom of the cast recess. It's nothing to be concerned about.
It's the raw casting. When the bores were milled, the milling didn't go all the way to the bottom of the cast recess. It's nothing to be concerned about.
the black spots are not an excess of material it's "missing" material, when I touch with tooth pick it goes down going over black spots not up, and it's rough.
Wish I can take better pictures...
p.s. the pistons are immaculate, was going to change them but they are perfect, not even a mark...
the black spots are not an excess of material it's "missing" material,
Exactly. When the part is cast, there is a rough bore cast in. The bore is finished by machining, and "the milling didn't go all the way to the bottom of the cast recess."
There is no chrome in the bores. You're seeing the difference between the raw casting and the machined, finished surface.
If you look down into the fluid passage at the bottom of the bore you will find the same sort of surface.
It's the raw casting. When the bores were milled, the milling didn't go all the way to the bottom of the cast recess. It's nothing to be concerned about.
Something like that, but it looks to me like they machined into voids in the casting. Which makes me wonder how that was cast in the first place. And it makes me wonder how that caliper got past QC. You'd think exposed imperfections on machined surfaces would be an automatic fail.
If that was on my bike, I'd run it without concern. But I'd also be a little miffed about it.
it makes me wonder how that caliper got past QC. You'd think exposed imperfections on machined surfaces would be an automatic fail.
If it was in a critical area (the side wall) it would be. As it is, all it means is the caliper will hold a fraction of a cc more fluid. There's no reason the bottom of the bore needs to be machined at all other than to ensure the bore has adequate depth.
I haven't done thousands of calipers, but I've seen exactly the same thing many times.
It's the raw casting. When the bores were milled, the milling didn't go all the way to the bottom of the cast recess. It's nothing to be concerned about.
Bingo!! we have a winner, all that kind of stuff is post machined after the coatings are applied. There's always small variation in the rough castings, see it all the time on the job.
03-03-2023, 05:22 AM
Rear brake caliper rebuild strange discovery
