Welcome. Was the generator run two years ago? If so, had it sat since then with fuel in the carburetor? Also, Have a look at the throttle linkage. Possibly a spring is disconnected and not allowing the governor to function properly?

 

It has never run properly. It did this from the moment we first tried to start it.

 

It turns over, fires up, and then the RPMs instantly rev way up, and it shuts off.

Check that you can move the throttle butterfly by hand. They're typically held wide open until the engine is started and the governor turns it down. Sometimes they get stuck in the wide-open position. I had that happen on a Coleman PM1500 and the VR capacitor exploded when the generated voltage went up to 300 or so. Just spray it with some lube and work it free if needed.

 

That gen has a stepper motor for controlling the throttle. It also has auto choke, but your problem is likely a bad stepper motor or its electronic controller.

 

or it is not put together right

 

Here is the wiring diagram for it...

 

Here is the wiring diagram for it...
View attachment 12081

Where did you locate this diagram?! I couldn't find diddly squat 😐