Pulsing Onan Microlite 2800
I have an Onan Microlite 2800 in my SMB. I have owned it about 3 months and I am trying to figure out all the systems. Generator is a Model 2.8KW FA26100G, Serial # C990872798. Its about 10 years old but only has 44 hours on the meter. It starts and runs well under no load, but when I put on the air conditioning or hot water heater or microwave the generator pulses, "rumm rumm rumm rumm", like someone is tapping the throttle. The voltage varies from 121-123 volts and the freq varries from 59-62. Its enough to make the light on the microwave dim with each pulse. I worry that this kind of thing is probably not real great on motors etc.
I have checked what I can see through opening the cover, air filter nice and clean, altitude set at 0, oil nice and clean.
There is an altitude adjusting know on the carb but it does not make any difference as to whether it is set at 0 or high altitude, still the pulsing. I can't find any kind of service manual on the internet so other than taking it in, I am kind of lost. I would like to figure out how to adjust this.