I've chased handlebar buzz and/or vibration on many bikes over the years due to a borderline carpal tunnel situatoion - singles, parallel twins, v-twins, triples, V-4's and Inline 4's.
First, let's be clear what we're discussing. Buzz is higher frequency stuff which leaves your finger tips or palms tingling, almost numb, feeling like a tuning fork. Those don't originate from an out of balance tire or steering head bearings. Vibrations are lower frequency and you would feel this in your hands, wrists and forearms to a degree. Lower frequency and higher amplitude....think of a Buell or a Harley shaking...that's vibration, not buzz.
If what you are experiencing is buzz and it recently started or at least got worse to the point it was noticeable...
Have you changed anything on the bike recently? Added any accessories that might mount to the frame or engine like skid plates or crash bars? Those can amplify a previously unnoticeable buzz or vibration and make it an issue. What about handllebars, same? Grips, same? Riding gloves, same? What else to check..
1.) Check your handlebars, loosen the mounting bolts and re-torque to factory settings.
2.) Check the clamps on the head to throttle body (TB) intake manifolds, make sure they are snug. Do the same for the intake boots between the airbox and the TB's.
3.) Check the TB's to make sure they are in sync.
4.) Check all of your engine-to-frame mounts for proper torque to factory settings.
5.) Check your exhaust bolts, starting at the head...anything loose?
Gen 1's have a bit more vibes and they worked on lessening this on Gen 2's with a redesigned clutch basket. I'll probably swap that out on my Gen 1 this Winter.
My Oxford heated grips also pass along a lot more buzz than factory grips, to the point I get pissed that I haven't removed them during the summer. Best option if f you don't have heated grips on your bike, I would strongly suggest buying ProGrip model 714's. No other grip I've tried since the mid 90's does as much to reduce felt buzz and vibration.
Good luck!