Fuel cock

Hi, I decided to fit a refurb kit to the fuel tap on my KZ750n1 Spectre 1982, thought I’d done a great job till I put fuel back in the tank and it poured straight out, I had the tap in the “on” position which is the position the vacuum is supposed to operate and stop the fuel from escaping, any ideas what I’ve done wrong? Thanks 

Did you put the small O-ring on the diaphragm and is the spring pushing it closed?

BTW, did you purchase the rebuild parts from Kawasaki?  Aftermarket petcock parts have a very poor reputation.

Hi, it was only a basic kit, I will strip it down and try again, definitely an after market kit.

In the picture it looks like the little oring comes pre-installed on the metal protrusion from the diaphragm. Be sure it is in place. Also insure that the little coil spring that keeps the valve seated was reinstalled. It is easy to lose and forget.
I always carefully polish the seat for the little oring as well as the face of the selection lever that seals against the big rubber bit that has several holes in it.