I've seen several posts recommending that a fuel resistant grease be used on the petcock's 4-hole gasket. Ordinary greases, including silicone grease, dissolve quickly in gasoline, so I searched around for a lubricant that is really "fuel resistant". I found a product called "EZ Turn", used in the aviation industry. As I understand it, it replaces an earlier product called "Fuel Lube". I got a 5 oz. tube from http://www.aircraftspruce.com/catalog/cspages/ezturnlube.php for $11.85, plus $3.65 shipping.
It's a bit thicker than typical grease, and since it doesn't dissolve in fuel, it will probably be good to smear on things like float bowl gaskets as a sealer/anti-stick. I may try it on one side of my clutch cover gasket, with sealer on the other next time I have that off. I would think it should be used in thin coats so a glob doesn't break off and clog something up downstream.
Great job of finding new products for us to use. 
I just figure if I find something I need for my H2, someone else might need the same thing. If it helps, it was worth posting. 