I woke the genset from its winter slumber Friday only to find it behaving worse than I do before my morning coffee. Gen is an '05 12.5Kw BEG model with about 320 hours on it. I’ve never had a problem out of this thing.
Through some Googling, I learned the generator is doing what's called "hunting." Under normal operation, it's supposed to run at a steady 1,800RPM. Instead, it's rhythmically fluctuating between 1,800 ~ 2,000RPM very rapidly, like a drum beat. It's doing this with no load and when loaded. While loaded, it's greatly exacerbated.
Spark plugs were new in the fall before initial winterization. Fuel tank was properly treated before winter and fuel is shared with one of my propulsion motors, which is running fine. Generator was winterized in early Oct, but then ran for 8 hours straight for our annual boat parade in December, where it performed flawlessly. After the parade, it was immediately rewinterized.
Thus far, I have performed the following to troubleshoot this issue: removed and thoroughly cleaned the carb; verified 2 built-in fuel filters weren’t clogged; checked governor oil level; changed governor oil (10w-30); cleaned linkage; inspected / cleaned distributor cap, points, rotor; adjusted idle speed. Fuel and delivery to motor is good. There's no unusual odors, fluids in exhaust (oil / unburned fuel), or sounds coming from system.
During all of this, the motor is not sputtering or running rough at all, so I'm compelled to think that there's nothing mechanically wrong with the engine, but possibly electrical.
I read that there's an electromagnetic sensor that counts the teeth on the flywheel and tells the governor how to regulate the engine RPM, however, I can't find that sensor. If that's not it, maybe the governor is bad altogether, but I've heard that's extremely rare.