Assuming you mean "shift lever" when you say "clutch"...
900 transmissions are pretty chunky on the whole. Straight-cut gears do tend to be noisy and give a solid "thunk" from gear to gear.
However, even with that in mind, I'd check the clutch lever freeplay. If it's too loose, the clutch may not be engaging all the way when you pull in the lever. There's a rundown on the procedure in your owners manual, and if you don't have one, you can download one at the Kawasaki website.
2011 Victory Cross Roads, crimson red
"There is only one God, and His name is Death. And there is only one thing we say to Death: 'not today.'"