[martin-csr]

The outlet on the rectangular cover is a vacuum port. Engine vacuum actuates a spring-loaded diaphragm to allow fuel to flow by gravity. When the engine is off, the spring returns the diaphragm to the closed position, stopping the flow of fuel.

From the diagrams at Partzilla the diaphragm assy is NLA. There are a few NOS on EB. I don't know if K&L has one for your motorcycle.

 

[martin-csr]

Partzilla is showing a vacuum petcock for the 1978 KZ1000-A2 but not for the 1000-B2 Ltd.

zhttps://www.partzilla.com/catalog/kawasaki/motorcycle/1978/kz1000-kz1000-a2/fuel-tank-kz1000-a2-a2a ... link disabled. delete the z at the beginning, then copy & paste into the address bar.

 

[martin-csr]

By kopcicle: and the plastic spacer is missing

Would that petcock have had it? I don't know & can't tell from the diagrams; a used petcock on EB doesn't have it either. I assume you mean a diaphragm plate. ??? ... Thanks.

 

[martin-csr]

That looks like a diaphragm only. When there's a plate, it's pretty obvious, since it's kind of thick & looks like plastic. ha ha.