With what little info is available, just some stabs here...
it's either gas or spark... and if it runs, I'd say it's getting gas, not spark. A cheap check is loosening the gas cap just to see if anything changes. I know, it's not the vent hose, but you never can tell. Check the fuel from the petcock to the carb, again cheap checks. If there's one handy, grab a crewchief who rides and ask him, for a beer of course, to take a look, crewchiefs will do anything for beer.
Good luck and keep us posted
