Yeah, yours looks the same as mine.
That grey metallic crust inside the sprocket carrier..

I've also noticed that my outer brake pad (the one next to the caliper piston) on rear is nearly worn, but the inner seems close to new.

I'm going to have a wild guess that my chain adjusters were out of sync (although i'm pretty certain I did them up exactly the same)

Still confused by this.

Everything is back together now, detergent in the hub to get it back together and a block of wood and a hammer!

The back wheel is a bit of a pig to put on when the rubbers are packed out like that! (working by myself, anyway)
It's just a few mm too wide!

In the end, I used the same block of wood to rest the tyre on, so I could hold both spacers, fit the caliper onto its runner and then stick a long screwdriver under the wood block to lever the tyre up into position using my foot!

Where there's a will, there's a way!

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Bike: 2013 XT660Z, TKC70 tyres

Mods:
Barkbusters, Scottoiler, DIY Tail Mod, DNA Stage 3, Power Commander V & O2 Eliminator, Exan X-Black Stainless exhaust, Tool tube, Ohlins linear front fork springs, Nitron rear shock, JT front and Supersprox rear sprockets, D.I.D. VX 520 chain, Adventure Spec bashplate, DIY USB Outlet, DIY chain guide, Kev's Throttle mod

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