I had a chance to work on it Saturday afternoon, prior to receiving most of the messages.
I drained the old fuel and put fresh fuel in with Sea Foam brand fuel preservative. It ran better under load than it had, but was still seeking a little with two high intensity shop lights hooked to its 110 V outlets.
I then cleaned the carb while attached to the engine. It has a bowl and when you remove the nut on the bottom, it exposes a plastic float with a brass needle. The tip of the needle is coated with a reddish brown coating that looked to me like it should be there. It didn't wipe off with carb cleaner. I shot carb cleaner in all the passages I could spot, and had brown colored gunk running out the carb.
After reassembly it ran better still. No perceptible seeking when the two halogen lights were hooked up. Now it was time for the disaster drill.
I cobbled up a patch cable to backfeed 220 through the welder's outlet and shut off the main breaker to the house, and all the individual breakers in the box. I particularly wanted to know if it would handle the 1.5 HP submersible pump for the well. It managed to run the pump and fill the tank, but the generator speed oscillated wildly when the pump was running, so the problem isn't completely solved.
While trying out different positions for the governor return spring, I managed to stretch it. I need to replace that spring since now the generator runs at 55 Hz, putting out 98 V without load and about
107-109V when a light is connected. Prior to accidentally stretching the spring, it idled at 60 Hz and with a light load put out something over 110 V and about 215V IIRC.
Not sure if the spring for my genny is a commodity item that a lawn mower shop would have or whether I'm going to have to really hunt for a replacement.
I probably need to replace that spring before I can do any further evaluation of how this thing is working.
BTW Wayne, in reading your comments from two of your posts, the carbeurator has a horizontal intake. The idle air mixture screw allows access to a passage, but it's a fixed screw with no apparent adjustment ability. It's just a square / blunt ended brass screw. Removing the carb may not be so easy. It's held in place with two studs that have a male star pattern on the end. I don't have a female star shaped wrench. I hope this helps to identify the type of carb that's on this genny.
Thanks for all the other comments too. Probably not a whole lot more I can do till I find a replacement spring.
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