Onan Gen Set 5000 very rough start

I just went out and tried to for an hour. . .no luck. I can make it "chugg" if I hold the start button. If i move the choke to fully open, it will "chugg" more violently, as I slowly move the choke it will "chugg" a little less violently. I tried to move the carb adjustment screws to 50 different positions with no luck. Could it really be as simple as a bad spark plug. . .it's getting gas, I have adjusted the airflow to every possible position. . it should stay running at some point and adjusted to the right idle speed, right????

Keep the help coming. . .I appreciate it!