Hey Tommy,
I don't think one gallon of fuel is near enough to break in a gas engine and make the switch to a 50-1 fuel mix. If your engine quits when you go verticle it sounds to me as if you're getting overheated, lean, or something like that. You may also have a fuel pickup problem. I hope your clunk is a heavy enough one to keep your clunk in fuel. There is no real reason for your engine quitting unless it is getting hot/lean. I would switch back to break in fuel for at least the recomended time from the manufacturer. I bet it's at least 6 to 10 hours run time which is way more than you can expect out of one gallon of gas. Good luck.