1977 CB750K petcock

[Hondaholic]

Good morning all.
I need to replace a fuel petcock on my 1977 CB750K, I have seen many aftermarket and stock offers but I am not sure of the mounting nut size? I have found some places that say 14MM and many that say 16MM. any help to do my own check.

Hondaholic

 

[amc49]

Don't go by nut, go by thread diameter on tank.

 

[Hondaholic]

Thanks amc,, that makes complete sense, I will do that.