Petcock bung KZ750 twin

I've got a leaky petcock on my '79 KZ750. What's the size of the threaded bung on these bikes?

I see some aftermarket petcocks that look about right and say they fit 22mm bungs.

Anybody know if that's going to fit my bike?

I remember looking for one for my 750 twin and concluding nothing existed. The experts who work at Z1 Enterprises might know if there is some adapter setup to an existing petcock. I have never seen one advertised.

These guys would probably know:

www.armbell.com/kz400/viewforum.php?f=73&mforum=kz400

I looked into replacing mine on the 76 kz750B1. As I recall 22mm for a Harley would work. I don't remember if it was pre 1995 or after 95. Most had a single line which I was going to put a T in. I had hoped to stop leaks and gain back the in tank filter. But a 82 kz750H3 came home with me and I did not make the purchase. this were aftermarket on ebay