Better to adjust valves for max clearance?

Hydraulic lifters?
Steve

Yup. Some years of the CB750 had them as well. The old Renault F1engines had hydraulic valve actuators (no cams or springs) that managed 20,000 rpm!

I've only adjusted valves on a KZ650 once. The lash was smaller or in spec on that motor, much like I find in the KZ550's. But from being on the forums, it seems more often, when someone has lash that has widened, it is on a KZ650. I wonder if there is some slight difference in 650 metallurgy that makes the gap widen.

What can cause the lash to widen? I don't think the valve is getting shorter. Is the bucket wearing away?

Other then wiping a cam lobe or just not measuring it right the first time, the only thing I can think of is carbon deposits on the valve head and seat.... ?
I can't remember 100% but I don't think I've ever checked a shim-bucket-cam gap and found the gap bigger then before....

Shim and bucket valvetrain systems are extremely stable. The bucket is guided by the head which reduces side load on the valve guide, and the cam wiping surface area is wide, which reduces cam and tappet wear. I don't think there is any way for the lash clearance to increase from wear under normal conditions, however there is always the possibility of some wear in the cam journal bearings. Variation in measured lash more likely relates to how the cam is positioned in the head, and/or how much oil is retained in the journal bearings. As mentioned earlier in the thread, if you use the 180* cam positioning method before checking lash the adjacent valve will be pushing up on the cam and skewing it in the journal clearance. This results in the clearance being greater than would be the case if you check the clearance using the factory kawasaki specified cam positions (which put two adjacent valves on the base circle). If someone was using the factory cam positioning method and measured more clearance than the last time they checked the valves than I'd blame the way the cam is positioned, and the amount of oil in the bearing journals in some way. I doubt the variation in clearance would be more than a thousands or so anyway, and measuring such a small clearance is always fraught with the possibility of measurement error entering the system.