Vibration

Well any inline 4 will do the 'numbing effect' to some degree. You're hands will feel numb after riding for a while at those RPM's.

I don't know if yours is worse then normal or not, hard to tell unless you can compare it to another similar bike.

It has something do do with the inline 4 setup, the timing of ignition, compression, etc.. Im not that mechanically inclined.

All brands have the same issue, not just Kawi.
Putting on thicker grips can help.

-=Welcome To Canada=-

2002 Green 6R
1986 Gixxer 7/11

There are many things that can help lessen vibration without going into the motor. The first place to start is with the bars. Heavier bar weights makes a huge difference. The ZX-12 has a really nice set of rubber-isolated units that are about 50% heavier. With the weights off, try pouring in lead buck shot into the bar ends (until full). I hate to add any weight, but if you want to cancel the buzz, I think you'll find this inexpensive and very effective.
Give the entire exhaust system a thorough examination. Most bikes develop some sort of problem here, especially with a less than ideal header installation. If the pipe touches anything other than the rubber mounts and the head mounting, the vibration goes through a bike very noticeably. There are several other things as well, but give these a try first.