BMW GS 1200 handlebar oscillation / vibration

[TheBear]

A Friend of mine took his 1200GS 2 days ago for his 1000km run-in check. Upon returning home he took it above 140 for the first time and from 160 upwards has a terrible vibration on the handlebars. Up to 200 it gets unbearable. Phoned the workshop and they reckon it is the wheel balance on the front that is out. Has the Metzeler Tourance Next tyres on it...

Wheel balancing seldom cause a vibration through such a wide speed range.