After not using for several months
There is your problem, Directions say 1/2 hour under 1/2 load every month. You did not do that and as a result the generator now has issues.
Suspects are fuel filter, carb and air filter, though that last one is down the list a bit, There are some other possible issues too but.. Those are the prime suspects.
I have seen fuel lines, and fuel pumps cause a loss of power in an engine too. But those are less likely.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times