The engine has 1 gallon and runs well. I haven't had a flameout problem when upside down, but wanted to prevent getting one since we have some slow turn marahalls. I haven't checked the plug in a few races.
The flameouts come only on refuel once my car has been dropped and I gun it. Half way out of the pit it stalls. Oh, on warms up I heard a sound twice like a backfire.