So, I'm doing my chain and sprockets today.

Haven't taken the sprocket carrier off in around 7,000 miles, I did take the rear wheel off for greasing before winter so I was expecting to see the cush drive rubbers a bit ******ed.



Actually, apart from separation, they don't look too bad. Packing them out with rubber really does its trick!

Going to change them anyway. New ones from AJ Sutton.



Well, as you expect, inside the sprocket hub is some horrible baked on rubber (*should have cleaned this out when I changed them last time!)

BUT also, what appears to be a crusty metallic residue.




It's all over the bearing, and inside the hole where the sprocket carrier meets the hub.

Some scuffing on the hub here:




So, it's cleaning up OK. Got the paraffin out and a toothpick for that baked on crud




But this metallic residue and wear does slightly concern me.
Any ideas?

I wouldn't have thought the movement of the sprocket carrier in the hub can create this sort of friction... There isn't enough movement with the cush drive all packed out.

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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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it looks ok now is cleaned up what you see is pretty normal the cush drives are poor ...
lots of guys use old bike inner tubes to pack them ...ive found that cushionfloor works real welll packem out use a bit soapy water and bang the sprocket housing in with a block of wood job done

Yeah, I've had the inner tube in there since I changed them about 7,000 miles ago.
And I know the rubbers disintegrate, not worried about them.. they're �20

But it's that dry metal dust that worries me.

You can see in the pic with the red arrow, that there's scuffing all around that hub and its receiving hole in the sprocket carrier.

These two surfaces are clearly rubbing together. It's not rubber crap like in the spaces for the cush rubbers. It's definitely a metallic dust.

That's going to be a pig to clean, as I hope it doesn't enter the bearing.
First thing tomorrow, I'll have a crack at that.

__________________
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

http://www.facebook.com/onemooseonemotorbike

I've also done this to my bike yesterday and I also noticed that metallic residue...
My bike has almost 20000km and this set of cush drive rubbers has almost 10000km. I've done the mod and now expect them to last another 10000km at least.
Here are the pictures:

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!

__________________
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

http://www.facebook.com/onemooseonemotorbike

Change them aside.

You bet! It has a pain in the ass to put the wheel in place. I'm also working alone...
I managed to do it using zip ties to hold the cush drive cover in place.

This is caused because of faulty wheel bearing (s).
For sure you need to change sprocket hub bearing, maybe also other two.

After how many kms (+/-) should we replace the bearings?
Mine as 20k km.

I die my sprocket carrier ones at high 20's (miles) but only due to them feeling notchy during a service. The wheel bearing had play in them at high 30's. You can tell by holding the wheel at 10 o'clock and 3 o'clock and wiggle it while sitting at 90 reg to bike. Any play at all and change them. Also if the wheel is off stick your finger in the hole and turn the inner race. If you feel any notchyness change them.

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***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!

__________________
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

http://www.facebook.com/onemooseonemotorbike