Need help with a generator

I have a brand new Duromax XL13000 duel fuel (gas and propane) generator. It will start just fine, but then it runs as if the choke is open and shuts off in about two minutes. The instruction book that came with it is....incomplete. No where does it tell you to look for a gas shut off, but there is one and it comes closed. Yeah, I found it but only because I knew to look for one. I can't find a choke. I know my push mower doesn't have one (or a manual throttle, for that matter) so maybe it's an auto choke? So, before I call Arnold Attitude in Commifornia (already had the pleasure once) I figured I'd ask here. Loads of experience with all kinds of engines. Any suggestions?