Another possibility (mainly for AK49er) is insufficient priming to get the air out of the fuel line from the gas tank to the carb. On many/most Onan generators, pressing and holding the "stop" side of the switch before starting the generator will run the fuel pump to prime the fuel system. Doing that for awhile (15-30 seconds, perhaps) before starting often will help initial poor running. This is especially true if the poor running is worse if the generator has sat for a relatively long period of time (i.e. one week vs. one day, for example).
The choke linkage/system could also very well be the problem, of course, probably among a few other possibilities.
