Clutch switch. Pull it and you can see the switch plunger. Squirt some light oil up there. Contact cleaner may work too, but it may also dissolve plastic. You've been warned.
Fuel petcock sounds like a vacuum issue. "Prime" is totally mechanical, the other two need vacuum. If brave, suck on the vacuum spigot and see if the petcock opens when on run or reserve (suck the fuel spigot). Best to do this on the bench with the petcock devoid of any/all residual gasoline though
Pull the plate off the petcock to reveal a labyrinth of small passages. Make sure all are open and free of foreign objects... like decomposing gasket material.
Leaky vacuum hose (or connection) to the petcock is also a possibility, the bike would kinda run like crap if this was the case.
Rick