There is a spec in the KZ1000 manual for how to measure cam chain stretch. I've forgotten the details and don't have my book in front of me, but here is a tale of woe that might help your thinking.
I recently restored a Z1B 900, having torn the engine down to the crankshaft. The speedo said 45,000 miles, so I thought time for a new cam chain. I knew I had a new one, but couldn't find it, so I checked the old one and it was within the stretch spec so I reused it. The chain was loose at the top sprocket idler but I figured it would be fine so I finished the rebuild and fired up the engine. Somehow it jumped the sprocket. In the process three valves were bent, but luckily no further damage. I ordered a new endless loop chain (and valves) and pulled the engine all the way apart to put in the new one when it arrived. Lots of work for nothing.
If you're really strapped for $$ and assuming the chain measures within spec I would try it and check the slack at the top sprocket idler. If the idler doesn't tension up on the chain I would replace it.
Here is a photo of the finished product.