During our Field Day 2008, we experimented with many power options. Since it is a well known fact many UPS devices are not compatible with the power generated by certain generators, we will report the combinations that work.
It is well known many models of UPS units do not like the power from motor power portable generators. Indeed it is a difficult task to keep the sine wave pristine when you don’t have the benefit of hundreds of square miles of the power network feeding you an almost infinite about of energy. Here is an example of the waveform from a truck mounted generator delivering much less power than its rated output… about 100 watts from a 5,000 watt generator.
The manual for the Honda EU2000 clearly states this, but you need to be sure you adjust that little circular knob on the Fuel Cap to the operating position or the generator will certainly quit after a few minutes operation.