Not sure which generator you are having issues with but our Onan has been 100% problem free, even has the original fuel filter although I have a couple of spares. I use the cheapest gas I can find as with all my motorized equipment (including vehicles) and have never run any of them dry. Both my onboard Onan and Champion 3100 inverter genny are just turned off and on as needed, never a carb issue with the Onan going on 10 years using 85/86 octane ethanol gas. I know many have had issues using such gas, my experience indicates this isn't related to just cheap fuel.
For the Onan I always add a bit of Stabil when refueling and maybe couple times a year a can of Seafoam. With the Champion since the fuel tank is pretty small I don't add Stabil but I do add a small amount of Seafoam to the 5 gallon gas can I use. Our rig goes pretty much unused for 4 months during the winter season and never an issue with the old stale gas, just prime the Onan for 30 seconds and she cranks up fine. In fact that reminds me to go out there and give her a little exercise while I'm thinking about it. Hope whatever is plaguing your genny is minor.
