How perfectly should my Onan run?

After taking all the other interventions I could, I swapped out the carburetor with a new one.

The singing of angels, gentlemen: A high and far-off song of joy, ten thousand thousand voices joined in ecstasy. It spins like a top, ticks like a sewing machine, purrs like a cat.

I honestly sort of eyeballed the speed and sensitivity after I put in the new carb, but even with "eh, I'll adjust it more precisely after I turn it on" the thing still ran perfectly. Eventually dialed up the speed just a smidge and tweaked the sensitivity for kicks; smooth response to adjustments, no surging at all, will take any load. My hz fluctuations went from +/-2hz when running "perfectly" to +/-0.5hz. My voltage stays within a single-volt range.

Wish I had replaced the carb earlier, but I didn't waste much money that wouldn't have gone toward thoughtful preventative maintenance anyway (spark plug, oil, new springs, some high-energy petroleum distillates, fuel pump, fuel filter: all of these things either strictly needed replacing or were worth getting anyway before I drove off to Nowheresville USA). Mostly just time and frustration, which I've got plenty of.

Notes, in no particular order:

• To replace the main governor spring, I backed the speed adjustment screw all the way out (counter clockwise) and put the sensitivity adjustment screw all the way in (clockwise). This collapsed the spring very close to its completely relaxed position and allowed me to install the new spring without stretching it very much. I then dialed both screws back to something like their original position before I started the genny again.
• On earlier repairs (fuel pump, control board) I went out of my way to clean the genset and replace bad wire terminals. This was helpful AND taught me more about what parts lived where. I also learned not to trust PO's wiring (the bad aftermarket fuel pump was not only bad, but was miswired; my Onan guys caught this right away, after which I snagged a wiring diagram and puzzled out the correct configuration).
• If there was a way to clean that KY Spec H carburetor, I tried it. I started out light, with Seafoam (many guys swear up and down that Seafoam is only for fuel stabilization and will not clear out gunk; I can't disagree), then with Berrymans B12, then with Birkebile 2+2 on a disassembled carb, then more Berrymans and Seafoam put through the running carb, then to a small engine shop's ultrasonic bath. The performance improved, but it never got close to what I'm seeing with the brand new carb. It's possible that these interventions will work if your carb is gunked from a season of fuel varnish, but I was staring down years of POs not using the generator at all.
• The control board was not fried when I bought it; I think I fried it when I was starting it over and over (with bad wiring!) to feed gas through the carb. If I had another chance, I'd replace the carb immediately; I think the control board would still have fried from the wiring issue, but maybe not. My symptoms for the fried control board were that the generator wouldn't even engage the starting solenoid, not even a click. The Onan guys diagnosed it, and when I saw what the board looked like, it was very obviously melted.
• The original starter solenoid, God bless 'er, is still perfect.
• I'll be stabilizing all the fuel that goes through the rig's main tank (which feeds the genny). Cheap insurance.
• It runs more quietly with the new carb, in addition to more smoothly. Adjustments to the speed and sensitivity also no longer cause wild reactions in engine speed and surging. This could be from the new springs, but I'm pretty sure it's the fact that the carb is healthy now.
• Armed with the service manual, a wiring diagram, the right tools, and a clean workspace, I didn't find any of the work I performed to be terribly difficult. My genset stayed mounted under the rig the whole time. The most fiddly part was replacing the main governor spring (it's pretty far back in there); the second most annoying thing was the struggle of manhandling the carburetor, the gaskets, the choke and throttle linkages, and the air filter housing all at the same time during carburetor removal and reinstall.

Thanks for the tips! Education is the most expensive thing in the world, but I still feel like I got a pretty cheap primer on small engine repair after it was all said and done. If you're in the same position reading this (old, poorly maintained Onan generator that is surging under many conditions), STRONGLY consider putting a new carburetor in it as your FIRST intervention. I'll hang around the forum to yell that at newbies :D