I’ve had two 640 adventures,both were a bit vibey,
Enough so that I sold the last one and won’t have another,
Big shame as I loved the looks and once on the dirt they were brill.
The other issue with a 640 adventure is the big tank has to come off to get to anything if needed and it’s a bit of a faff.
I’ve also had an early 690, the limited steering lock put me off that fairly quickly.
But it’s a excellent bike apart from the stupid lock.
I’ve heard that the frame etc is different on the later bikes ,but haven’t ridden one so cannot confirm if the amount of lock is improved.
The bike I most regret selling was the 525 exc,
I sold it to buy the 1st 640.
I’d be very tempted to modify one to build a travel bike like andy’s huskie.