The typical in-line 4 has inherent vibration at 4000-ish, but my 2016 is worse at higher rpms.... I'm running a 16T front sprocket, so that makes it 5500-6000-ish. IMHO the biggest influence is uneven firing of the cylinders...... here's what I did recently....
Valve check, intentionally reshimmed all the valves to be same uniform clearance (as best possible) and at ~70% of max tolerance (I don't want to go in there again very soon, lol). Uniform clearances give you the best chance, followed by a good throttle body sync, since that is affected by valve clearances. The results are noticeable, my 6000-ish rpm buzz is minor now and it's a higher frequency than the minor vibe I feel at 4000-ish. I used to get tingly buzzes in the left footpeg and a bit in the handlebars starting at 5500-ish.... much much reduced.
One can adjust the balancer shaft, however, you're not changing the phase of the balancer, just the engagement of the drive gears. Shouldn't be much effect, but maybe, I haven't done that yet. No harm in those drive gear clearances being at minimum..... just follow the manual's procedure.
