I know of no standard voltage regulator (non inverter type generator) that likes to push a field when the generator is operating slower then 55 Hz. This is referred to as the "Cornering Frequency". Starting up under load can push power transistors well beyond their limit. Via inductance, a fully saturated stator can actually pull more amperage through the rotor coil than what a simple ohm resistance test would imply. Will the engine start? More probably if it has excess horsepower to wattage ratio. I've never had an opportunity to fiddle with an inverter generator to see it's loaded start up characteristics but judging from the large amount of troubleshooting questions and answers full load starting probably isn't very wise either.
When frequency hits 55 Hz conventional voltage regulators go nuts.