I hate champion plugs, but that's a rant for another day.

Are they rich across the board, or just at certain throttle positions? If you slowly roll up on WOT in 3rd gear or so (because dumping the throttle will feel rich every time) how does the bike feel? Does it bog, or does it pull pretty cleanly all the way to the top? As you roll on the throttle does it get better or worse? You need to do some WOT plug chops. That's where you get it running WOT and high-revs (7k or so) and kill the ignition/pull the clutch in without letting off the throttle first. Then take your plugs out and see what they look like. If it's running good at the top end, then it's just a needle-position issue. You gotta dial in the top end first before you try the mid and finally the bottom.