Run 8 range plugs. Go up 2 sizes on the mains...check the plugs again.
Are you warming the bike up on old plugs, going for a WOT run, then pulling the clutch, holding the throttle open and coming to a stop, then removing the plugs?
Are you winding out at least 5th, if not 6th gear?
If you are doing it properly, bump it up two sizes, chop again...keeping in mind, once it warms up, you'll probably need to jet down a size, maybe two. You're very, very close...