[reclinedrelic]

I don't see anything about the petcock there, though.
Of course, the whole problem can be eliminated by converting to a non-vacuum petcock.

If you are referring to Hann's site the page I gave a link for gives instructions on disabling the vacuum function, converting the petcock to non-vacuum type. I believe that is to what phantomcxmenace was referring.

 

[Sidecar Bob]

Now how did I miss that?

Anyway, I couldn't recommend bypassing the vacuum valve on an ancient petcock either because the wafer is likely to be rock hard and probably needs the vac valve to keep it from leaking while parked.

 

[CXPHREAK]

I don't have vacuum petcocks on any of my bikes. If not used for a week, 2, 3 weeks they generally just start on the button the first time anyway.

I leave my petcocks on. Any fuel that evaporates is replaced as it evaporates.

Reluctance to start isn't normal. It's a shame the vac petcocks don't have a purge position like those on Suzukis.

 

[joethebike]

My vacuum fuel tap is original and functioning properly and as my bike is usually idle for a week or so before having a ride an infallible technique to ensure a quick, stable start is to drain the bowls then detach the vacuum line at the tap, plug a length of hose onto the tap's vacuum post, suck the hose until the bowls fill (transparent fuel filter shows fuel flow), reattach the carb vacuum line and voila, instant start.