Does your generator have a single fuel filter or 2 filters? Our 2001 Adventurer originally came with 1 fuel filter at the pump, and a second screwed into the carb. Onan later eliminated the one at the carb because after it was replaced a few times the threads would often start to leak.
They came out with a fitting that would replace the filter and remain in place permanently. Later models came only with a single filter at the pump.