this is going to be a question I did answered also. a friend of mine said he went out to the garage to exercise his genny and it would only start running after he gave it a shot of starting fluid. at first he thought the carb was gummed up but he always runs it until it runs out of gas in the carb, so we ruled that out, thought it might be the spark plug but it runs OK once you use the starting fluid so we ruled that out. only thing we can figure is the cold is doing it. some motors are just ones that hate to start once it gets cold out.