Justin........this may sound simplistic but how much fuel line are you useing to get from tank to engine? I have a Sig Morrisey Bravo running a US Engines 42cc with a
Walbro carb. The tank is not easy to get to so I used an extra long length of tygon the extra was wrapped in about three loops right next to the carb. As long as those loops remained full of fuel everything was ok, if not I could not get the engine to start without priming the carb several times. I removed all excess tubing and now it starts easily and runs great. Hope this helps.

Gene