86 VF500F Petcock vacuum assembly missing.

I'm still sorting my 86 vf500f . After having the carbs rebuilt to factory jets/adjustments starts runs but It seems to be suffering from fuel starvation. I found the fuel petcock vacuum diaphragm assembly was completely removed at some point. I know what suppose to be there but somebody thought it wasn't needed I guess. Is it? I'm not sure where the vacuum hose is suppose to connect with the carb vacuum either but I guess that's a different problem. Thanks in advance for any info.

 

I doubt a lack of vacuum cutoff would impede fuel delivery. My guess would be either float heights or clogged jets/airways. To what degree was your carb rebuild?
My petcock had similarly been modified. I reinstated the vacuum cutoff. The vacuum takeoff is a nipple off No.1 carbs manifold. You probably have a blanking screw in there like the other. If you want to reinstate the cutoff the whole assembly is still available. It will prevent flooding your engine if one or more float valves fail and the petcock is left open.