***UPDATE***

My local Yamaha service technician reckons that as the cush drive perishes, this will cause the two metal parts to grind together..

I told him that the rubbers hadn't really perished that much in 7,000 miles due to the ol' inner tube trick.

~When I mentioned the bearing, he said this shouldn't be going until at least 20k miles.
(This is a bike that is doing 80 miles a day in all weathers.)

I'm going to go with replacing the sprocket carrier bearing.
Also overhaul the caliper at the same time.

Thanks for all the advice, Tenners!

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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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