[Rich Biebel]

Fuel filter would be the first thing to change.
Check fuel lines and fittings....cant have any loose fittings that allow it to draw in any air.

Oil too full....It only takes 3 qt's...

Engine speed is controlled by the control/inverter and powers a stepper motor on the injection pump.

Kubota 3 cylinder engines are generally very reliable.....

Its an odd scenario.....

Clean fuel, no air in the system and no restrictions like in the filter. They are pleated paper inside and can get very bad....

I sometimes advise people to drop the fuel lines in a 5 gallon can of fresh fuel right near the generator. See if it makes a difference. Helps to eliminate issues with the fuel tank and lines.....I've seen problems there.

I recently had someone call with a 10 or 12 kw Onan that would not start. It had been sitting a long time......

Injection pump rack was stuck internally.....fuel could not be supplied to the injectors....