i can say in my 450 i have noticed a TON of flakes every time i do an oil change as well.
One of the local shops here actually ran some 525s for 2 years and said the noticed the same thing.
What i actually think it is, is the little metal dowels inside the clutch that rubs up against the pressure plate, amongst other things.... now whether it should still be doing it 3 years later......not sure, but mine is 1 year old and most definitely still does have a ton in there everytime.
* Spode Freestyler *
Team Spode Racing
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2004 YFZ450