Leaking fuel Petcock

My kz650 was leaking fuel so I pulled the petcock and ordered a rebuild kit. When I installed the kit I noticed a few things that don’t make sense. 

First of all, the fuel selector lever is not held firmly against the rubber seal behind it. It appears the plate with fuel markings is meant to hold this in place, but it actually allows the lever to be pulled out just enough that the rubber seal behind it isn’t able to properly seal. It’s almost like the seal is .030 too thin. But I put the original back in and it still had this issue. Very Strange. 

Second, after installing the petcock with all new parts, it still leaked. I was able to verify this is due to the internal spring not pressing enough on the diaphragm. The fuel was leaking by the o ring as it should when vacuum is applied and the diaphragm compresses the spring, even tho there was no vacuum.

The spring is installed correctly, but on a bench set up I was only able to stop the flow by using my thumb and putting force on the diaphragm while the cover was removed. Far more force than the spring can exert. 

I even went back to the original o ring and diaphragm, thinking maybe the rebuild was junk and too large or small and wasn’t fitting correctly to make a good seal. Same problem. 

honestly I’m amazed it didn’t always leak, but it worked fine until this season. 

I bought a new OEM unit to replace this one. But I’m just curious if anyone knows why this one is leaking. 

the pictures are the petcock. The one with the fuel lever off is showing the rubber seal. 
 

Did you polish the seating area that the oring is supposed to seal against? If there is any pitting or roughness in the surface, the oring will not seal well.

Also, there should be a spring washer between the retaining plate and the selector lever that forces the lever against the oring.

www.partzilla.com/catalog/kawasaki/motor...uel-tank-81-82-h1-h2