Question for ya. You've said "GPZ" but haven't said which model.
Sometime in the early 1980s, maybe even late 70's, Kawasaki started using something called the "Clean Air System" which is a little gizmo that draws a bit of extra air into the exhaust ports to allow combustion to finish in the exhaust header pipes. (They still use this system to this day - and the other manufacturers all use something similar.) The good thing is that this reduces pollution by helping the unburned stuff finish burning. The bad thing is that if you do exhaust analysis on the engine, you are not actually seeing what the engine is getting ... you are getting a false reading which is slightly leaner than what the engine is seeing because of the extra air that this system draws in.
On top of the valve cover, there will be a couple of hoses connecting to a little contraption sitting directly above the valve cover which in turn has another hose leading to the airbox and a little hose leading to a vacuum port somewhere at the carbs. That contraption is the valve that makes this system work. To get a proper reading on your air/fuel gauge of what the engine itself is seeing, you need to plug the hose from the airbox that leads into this gizmocontraption.
You can install fancy looking block-off plates to eliminate the gizmocontraption completely, but for testing purposes there's no need. Just pull the hose off the airbox and jam some suitable object into the end of it to plug it (in a way that you can get it out again afterward) then stick the now-plugged hose back on the airbox so that you don't have an air leak at the airbox. You can put the plug into the other end (at the valve in question) if it's easier to get to, makes no difference.
14.2 at idle is good. 13.8 under moderate acceleration is also good. 13.8 at full load IF KCAS is plugged or blocked off is a bit lean. If KCAS is still connected and working you may end up finding that it's actually a bit richer than that once you disable it to see what the engine itself is doing. Air cooled engines don't like being lean under load. It should be mid 12s at full load acceleration with KCAS plugged. (and if it runs happily right now, you might find that it's already there once KCAS is plugged)
Needles should normally be set to the leanest setting that gives smooth operation. If you can get it to be 15:1 at steady cruise (with KCAS plugged) you'll be happy with the gas mileage and range, and you'll get less fuel dilution in the oil.