I assumed it was where you got your model ID photo from. The site has a large Kz400/440 model identifier page.
I just go to Kz400.com. It used to be a full-fledged forum etc. but it's a lot of work and money to keep that up, and after Odd Ivar passed away, other members kept it going for awhile, admirably, but I think it was just too much work and cost to keep up. Now it's more of a simple webpage. Some reported viruses on the downloads there, but I've been on the site and downloaded manuals without problems as recently as last year.
This is a link to the 1978 workshop manual, but I haven't tested out the downloads for that manual.
Maybe download the manual to a phone or something to see if it causes a problem. Or perhaps someone else could chime in on how safe the manuals are from that site.
I have a question about something that I discovered last night:
There are 2 holes in the top of the engine case that look odd to me.
I'm surprised that they don't have a plug to keep dirt out.
They are from the factory.
The large hole just lets water and gas drain out to the chain area to drop out under the motor.
The small holes (there are actually a few in that area) are just the bore-through for threaded holes that hold bolts and screws from the other side. They can get dirty without issue. They go into an area that is likely dirtier than the part you can see.
There is another post on this exact question. It has photos if you want to see the backside of the casting without taking the sprocket cover off.