Ok to let cam lobe touch empty bucket top ?

On a KZ1000 when swapping shims around to set valve clearance. Is it ok to let the cam lobe
push on the top of a lifter bucket without a shim in it ?
I just don't see any way around that unless you just stuff a random shim in there.

Never.

ok

There is no need to rotate the cam lobe over a bare bucket. Assuming you don't know what shim is currently in place...

1) measure your clearance
2) depress the valve with the cam lobe, use the Kawasaki tool to hold the valve down and rotate the cam a half turn or so...just enough to allow removal of the existing shim.
3) pull the existing shim and check its thickness...should be written on the side facing the bucket but if not use a micrometer
4) select the appropriate new shim based on your clearance measurement and the old shim thickness and drop it into the bucket. Be sure it's properly seated.
5) remove the Kawasaki valve depressor tool...exhaust valves will require counterclockwise (backwards) engine rotation. Intake valves will require clockwise rotation when viewing the ignition timing bolt.
5) rotate the cam over the shim a couple of times and re-check the clearance.

I recommend keeping a record of shims and clearances along with the date they were last checked. I use an excel sheet on my computer.

Edited to add that you should always try to put the side with the number face down. I usually forget and am disappointed when I pull a shim with the number worn off.