As an owner of a 20 KW air cooled generator, I read this forum frequently and note the negative comments by some of the Generac product. For many years before getting my Generac, I relied on a Honda EM3500. I took very good care of the Honda but it has let me down. It needs a new stator costing $825 for the part. Now I have a very good engine which is not good for much else as it has a tapered shaft. Buying the shop manual provided the diagnostic method. Remove all the electronic voltage regulation and power supply to the rotor winding. After verifying the resistance of the rotor and brushes are within spec, hook a 12 volt battery to the brushes and check the output voltage of the stator windings. A simple pass fail test.
Many see Honda as a top notch product but they too have problems.

Dave p