DIAGNOSIS Varnish from old ethanol gas has clogged the pilot and main jets in the carburetor.
FIX Use a carb cleaner additive first, then manual cleaning if needed.
1. Drain all old fuel from the tank and carb bowl (use the drain screw on the bottom of the carb).
2. Add fresh 87 octane fuel mixed with a high-quality ethanol treatment cleaner (like Sea Foam).
3. Run the generator for 20-30 minutes under a moderate load (like a space heater).
4. If it still runs poorly, you must remove and disassemble the carb to spray cleaner through all jets.
IF THAT DIDN'T WORK The ethanol may have degraded the rubber diaphragm in the carb's fuel pump. A full carburetor rebuild kit is the next step.
HEADS UP For storage, always run the carb dry using the fuel shutoff valve, or use fuel stabilizer. Ethanol gas is the root cause of 90% of small engine problems.