1973 Onan 5CCK 5kw Generator - Why Don't You Start?

I bought this 1973 Onan 5CCK 5kw 120/240 volt generator January of 2020, right before Covid hit (I also have an old, loud Generac 120/240v 5kw generator from the 90's but got on the Onan 5CCK kick in 2019). I use this Onan when the power goes out. It's not terribly fuel efficient so if I don't need to run the 240v well pump, I can get away with using my Pulsar 2kw 120-only inverter generator to run the house if I switch off all 240 volt circuit breakers and make sure the two laser printers in the office are turned off (they take a ton of wattage when they first come on).

Anyway, it's probably been two or three years since I started up the Onan 5CCK so I figured today was the day. It managed to start after several tries with the starter button and ran for a minute or so but then started missing and finally died. I don't have a recent photo of it but the below one is shortly after I first got it. I added the little grey box on the side of the switch panel, which shows volts/amps/hertz of each 120v leg.

Jupiter Discovery X5 E-bike - Adding Onboard Power to Tail Light

Something a little odd with this bike is that the rear tail light runs off a 3 volt button cell rather than from the main bike battery like the headlight does. I wanted to rectify this situation so I bought what's called a DC-DC Buck Converter, or Step-Down Converter. It will take 40 volt bike battery voltage and step it down to pretty much anything you'd like. In this case it will step down to 3 volts (or 12 volts as you will notice further down the blog). Here's a photo of the converter. The small rectangular blue thing is an adjustable potentiometer which is used to adjust the output voltage.