Coleman Powermate 4200 Generator

I have an 8hp Briggs and Stratton engine 197412-0124-01. I cannot keep it running without closing the choke. Leaving the choke wide open will cause the engine to die. I replaced the gas lines, gas filter, rebuilt the gas pump and replaced the carb (not with an OEM carb). I’m running premium gas in it. I had the tank off and made sure that was clean. I changed the oil in it as I think the old carb was putting gas in the oil. I also put a new on/off switch on it as the old one broke. I am at a loss of what could be wrong with it. Any ideas what the issue could be???? Thanks!