Don't ignore any of the following:
Wear / play of stem bearings AND cups/races.
Front tire (wear and air pressure).
Front forks, although if I remember the bushings are non-serviceable.
Front wheel bearings.
Fork fluid levels/condition.
I had a minor occillation on my 08 when I got it. Several front tires, new stem bearings and wheel bearings and it was good to go. Also did the fork service.
That said, it is probably the front tire.
YMMV,
Barry