Confused about my fork caps (KZ440)

I'm dealing with a box-of-bits KZ440A1, and am in the process of putting it all together. However, I've hit upon a snag. Wondered whether any of you guys might be able to shed some light on this? I'll describe the issue.

Fork caps: standard screw-in chrome fork caps. No problem. I unscrew them. I expect to find, underneath, a slider/spacer (part number 44029022 as per the parts diagram) held in by a circlip. But I don't! Instead, there's a second fork cap there, underneath. The second fork cap is black, it's  also screw-in (uses the same thread as the shiny fork cap tops) and has a square indent for a 12mm-ish tool to wind them in and out. A 1/2-inch drive wrench fits in and lets you screw them out and put them back in again. Underneath this secondary fork cap there's just the fork spring.

Problem is, one of these secondary screw-in caps failed on me (I was probably putting it in not quite square), and has now stripped its thread. No matter, I thought, I'll look up the parts diagram and buy another one. To my surprise, no parts diagram for KZ440 shows this part. I looked up the KZ400 parts as well. Nothing. Same as for KZ250. The standard bikes, according to the parts diagrams I accessed on cmsnl, appear to all use a circlip-and-plunger arrangement under the main (chrome) fork cap.

Now, I was thinking, if I reassemble both forks with the standard plunger (without circlip) plus a spacer, and rely on the topmost fork cap to hold it all together, it would probably work. But I'd rather not deviate from the manufacturer's design, especially as the topmost fork cap isn't designed to hold down the spring pressure. 

Does the fork cap arrangement I've described ring any bells with anyone, and if so, have you any pointers as to where I could get one of the little internal screw-in fork stoppers to replace the damaged one?

Thanks

I have no clue as I never heard of such a setup but if I had to guess… I’d say the inner cap was a way of setting pre-load seeing as there’s no spacer underneath. So if your top cap has an o-ring, I can’t see a problem substituting the inner plug with a spacer and washer.
Do it on both forks.

Preload adjuster makes perfect sense - thanks. 
I suspect the forks are from a Japan-market-only model, which is why I can't find that part on the parts diagram. The top cap does indeed have an O-ring. 

Just shooting  in the dark here...Could it be that they are not Kawasaki forks? Pics would help here.

Well, I reckon they're definitely preload adjusters (as they were not tightened down but were somewhere midway down the thread). It's a definite possibility that they are not Kawasaki forks. Do the standard ones have a progressive spring rate (smaller coils at one end)? Because these ones do. The stanchions seem to be the right length and the brake caliper is a Kawasaki one which fits perfectly, although the mounting hole separation distance may also be one that's shared with other Japanese makes. The front wheel is also a 7-spoke Kawasaki one, although that doesn't mean much, given that if a previous owner had changed the forks following a collision, the collision might not have been hard enough to damage the wheel. I agree it's odd for a Kawasaki standard fork of this age to not have a circlip and plunger.