I just recently mounted my engine. I have ran it a couple times. But now all of a sudden it has started flooding bad. The engine is mounted with the spark plug down and I have a return line going back to the tank. The tank looks like it is starting to implode a little from suction. Should I put the return line outside of the tank or should I loosen the tank plug so it can breathe?

The tank HAS to vent to the atmosphere, run a vent line.

Thats what I thought, the tank instructions did not cover that. It has an extra hole in the plug that the manufacturer said was for a filler line. Guess i'll use it to vent.