Originally Posted by blk-betty
Hmmm, not my experience with several HDs, a DR650, Triumph 1050, and Honda CB 650.
Honda Varadero 125, CBF 600, NC 700, VFR 800 46/2, VFR 1200 and Kawasaki ZZR 1400 here - and I want to count the 686ccm single of my Grizzly as well. In my experience the I4 engines are quite smooth at every rpm, the V4 ones are quite rough at low rpms expecially when you try to accelerate.
The 2 cylinder engines don't have that huge difference between high and low rpms but aren't as smooth as the I4s in general. Well and the single... it shakes and shakes and shakes but shakes a bit less in the high rpms.
The BMW R1200 boxer maybe is the most extreme one - I thought it would fall over from the vibrations when I started one for a test ride and let her idle. Got a bit better on the move, but not much.