Short story version, the anti-slop spring on the throttle mechanism was bent enough to upset the spring balance and allow the throttle flop back and forth ever so slightly. So it would surge a little. I was lucky that straightening out that spring fixed the surge. I'm sure that's when the throttle setting got messed up. I pulled the gas tank and completely cleaned the carb trying to solve the surge. I was running the generator with the tank off to the side and noticed the linkage open and then get pulled closed and realized the anti-slop spring was pulling too hard. Sure enough it was bent which effectively shortened it. To set the frequency, Generac service manual says to set the engine rpms at 3600. I don't have a tach so I just watched to no load frequency until it was back below 61 Hz.
I try to save money where I can and this generator may well run my layout some snowy night.