I had a ninja 650, first year. The buzz i eliminated by riding without the lower fairing. I had the bike apart a dozen times, fitted foam, the dealer kit, to no avail. Check the tig weld on the right motor mount. There were frame failures there, as the spacer originally put in by Kawasaki was a bit too small, torquing the motor mount bolt drew the mount in closer, and in use, it failled. The crack might be on the top side of the weld, btw. I accelerated the process by totalling my bike, and when the motor hit the road on the right side, it cracked the motor mount as described. Bad design, IMHO.