It really depends on the condition of the Carb-today, the oxygenated Fuels that we are sold are diferent than just a year ago-Gas can go bad in just a few Months now-
anyway, I would pull it apart and see if it's just clogged or if it's corroded-if it's corroded, I would find a good Onan Dealer and replace it-
try these guys-
http://www.coloradostandby.com/catalog/index.php