Your tank is too big and too high. The top of the fuel level shoudl be even with the needle valve. It's also too large in my experience to ensure a consistent run. Something at 1 to 1.5 oz is as large as you should really go with. Or run it off a bladder tank so the pressure makes up for the larger fuel amount.

If it doesn't start then it's either dry or flooded. If you listen to the sound of the sizzle from the plug through an open exhaust port you can tell if it's too dry or too wet but close to starting. If it's a dry sounding sizzle then add some prime. If it's a wet sounding sizzle with crackles then it's too wet and you need to prevent any more fuel getting into it and burn off what is in there until it starts