I'm no MOB or SISF(IOW, I only wish I had their skills), but I have had many carbs apart of many types. The Onan carb is the one weak link on this gen set. When I get a 20 year Onan tech tell me a new carb is the answer, I ignored him, tried yet again to clean the carb. I used the full RV fuel tank (yes, 35 gallons) to cut my grass, even burned some in the dirt bike. Finished emptying the tank (Stabil for Ethanol added), added fresh fuel, ran fuel pump until it was clear and no signs of contamination. Fresh fuel added, super (I thought) clean carb, same issue. Gave in and bought new carb. Installed, runs perfect. I will use a magnifying glass to see if I can spot the blockage so I can have a backup carb, but that will be a winter project.
As to adjustment? There is an altitude adjustment screw with one of those stupid plastic caps to limit how far. Removed, cleaned needle and seat, reinstalled, and still, no love. There is also a fuel shutoff solenoid on the bottom of the carb, bottom line? I gave up, for now. I have a 24 hour race coming up and I needed everything to work smoothly so I can focus on the race... And then there is elk season