Disconnect both lines.
Fill the tank with the carb line until you see some fuel come out of the muffler line.
Take a little bit back out at that point (1 turn or so on a manul, a second or so on an electric pump)

Make sure you don't have the lines crossed.

You shouldn't be flooding, those rear mounted needle valve engines are a pain to keep from fuel draining back to the tank as it is, I've never seen one flood unless your holding your finger over the muffler and cranking the engine for a while.

Might want to pull the glow plug and spin the engine with a starter to clear it out if it is indeed flooded.