I'm trying to figure out what is happening with my fuel supply. My '97 won't run when connected to my tank. When removing the tank the carbs are empty. I hooked up a gravity fed tank to it and after the carbs fill up the bike runs beautifully and easily empty the 200ml tank. It also starts with no choke at all and is just running beautifully. So, with the tank on a bench and with the fuel lid closed and locked, I applied vacuum to the petcock. It had no trouble draining the contents, ~3 gallons. So the petcock is good, the cap is venting properly and there's no large clogs. I'm not sure where to look next. I recently replaced the fuel filter, fuel line and vacuum line. Could the fuel line be too long and possibly kinking or looping over the height of the petcock's outlet preventing a gravity fed feed? The only thing I can think of that I haven't tried is hooking the tank back up to the bike and manually applying vacuum to the petcock. Any additional suggestions would be greatly appreciated!