lol i wasnt kidding. i dont mean ride and blow it hahahaha. i mean put it on the stand go WOT while blowing it.
now that i understand your situation better im thinking its your petcock being clogged.
your petcock may be clogged a slight bit to the point that. whatever .4 gallons weighs isnt enough pressure being exerted to push that gas through the petcock. the weight of more than .4 gallons may be whats pushing the gas into the petcock. you might need a tank cleaning. pull the gas line off and see if it flows. it might flow but not fast enough to feed the engine for extended periods of time. drain the tank take out the petcock look at the filter on the petcock. then try to clean it with carb cleaner or something. it might save you from having to buy another petcock. then get some acid stuff to clean your tank mix with water. remember always put acid in water and never vice versa
and then skip the kreeming part. rinse it out with soap. and water. then water. then let it dry. you can use a blow dryer but i broke mine in the process. then test if petcock will flow enough by running water through it. if it does then you can use it i suppose if its dirty beyond repair go get a new petcock. either way a new petcock will benefit you most. unless you really needa save money. then put some fresh gas and oil mix in there and run.
this is all assuming you have a dirty rusted tank and cloggged petcock. if not then i just type a whole lot for nothing