Sudden change in clutch action

[Ruby Racing]

Either your hand has suddenly become a lot stronger or some debris that was obstructing movement has cleared. Neither of these sound very likely.
The other possibility is that something's broken in the clutch itself, a failed spring for example. Since road conditions haven't been ideal for flat-out acceleration recently it's possible that a weak clutch would go unnoticed other than at the lever. 8500rpm with the throttle fully open should provoke clutch slip if one of the springs isn't working.

I concur.