I would guess it has a low voltage winding, maybe around 10 amps, 20 if you’re lucky 
He uses a Kill A Watt meter, or something very similar. If +/- 1Hz is good enough, then it’s a simple solution, and really useful for lots of measurements.
edit: Checked the video, and it is a Kill A Watt meter, and it reads to a 0.1Hz. That ought to do it. Though a permanently installed freq meter would not be in the way.
RindertW. the DC-out charging capabilty is from a small set of separately wound coils. That rough AC generated is then ran through just a small bridge set of diodes. VERY low wattage. 120 watts, usually at the most. And the DC out voltage is relatively dirty and NOT voltage regulated. Should only be used to charge up small, thick plate small engine starter batteries. For real, faster, battery safer, four-step-voltage capable battery charging use a good separate dedicated charger from one of the much higher wattage outlet ports.
Disposing of contaminated gasoline?
Depends how much gasoline you need to get rid of.
Depends greatly on where you live; your household mates; your neighbors.
Depends on whether you strictly want to abide by your areas current evolved legalities.
Last time over 20 years ago now in professional Urban area shops it was then $10 a gallon to have pick up for disposal. And someone had to sign their signature on the head of the recorded chain of custody tracking. Go cheap on the contractor; and it got ditch dumped; and it would track back to you the originator, signer.
I expect that price now will be double, triple now.
True Rural living we would store it and at an annual woody debris bonfires time pour it over the pile a day or so ahead of time. Wait for the majority of the volatiles to evaporated off and then in Early Cool of the Morning FROM A DISTANCE lite off the burn pile.
Other ways too. Most not exactly legal. The rule of the three iLL’s applies here.
James Cordon did say he would wait for the majority of settling separation, then burn it up the least contaminated portion in an IC engine. Your older generator would be the candidate for that.
Just please don’t dump it directly onto the ground. Irresponsible.
Regards
Steve Unruh
My TLUD, for charcoal making, seems to burn wood tar with almost zero smell. And my neighbors are used to me making charcoal. I think I’ll try soaking some wood chunks in the nasty stuff and then put them in the TLUD. Hard for me to crud up an engine even if real old.
Rindert
When I was doing ironwork it was common practice in the winter to fill half of a 5 gallon metal bucket with gasoline and then light it as a source of warm up heat. Surely things could have gone wrong but I never heard of anyone getting burned from the practice. If diesel was on hand we would use that the same way.
