where I remarked on the amount of crepe behind it,
Well I just changed my sprockets on the 748. The amount of crepe you see when you remove the cover is just the tip of the iceberg, compared to the amount revealed when the sprocket is removed completely!
Quite a while back a bought a QD rear sprocket assembly. The rationale behind that was not that I wanted to change gearing frequently, but that the QD design would, in the future, mean the difference between paying labour charges to have the stock sprocket replaced (a fiddly job), and replacing the QD one myself, a simple DIY job. Not to mention the QD (Talon) sprocket is 22 quid, whereas the stock one is... how much?
And so it proved. Rear sprocket came off no trouble at all (I'd thought it might be a very tight fit on the carrier, but it wasn't).
Biggest job was cleaning all the gunge out from behind the front sprocket. That took by far the biggest proportion of the time. I reckon I've lost weight, in mud, equivalent to a grand's worth of titanium fasteners!
Last time I tried to do this (I was running stock chain length and 38t rear then), I seem to remember I had trouble getting enough slack in the chain to unmesh it from the front sprocket. Managed that this time OK, though.
But that front sprocket only *just* comes out past the chain (that's after having removed the clutch slave cylinder). I'd imagine getting a 15t one on and off could be a bit of a pig.