Just did a bit of homework on this unit and spoke with the generator repair guy who originally looked at the unit for the owner.
Turns out the genhead has a bad exciter field winding.
He also said the enclosure wasn't designed to come apart, so there are parts of it that are going to have to be cut in order to get the generator unit out to work on it. He felt it was not worth much beyond scrap due to the time it would take to get it apart, repaired, and put back together. Now maybe he wants it, but he didn't seem interested in it based on how he sounded - just very matter-of-fact about it.
I called my local rewind shop for a ballpark estimate to rewind the exciter winding and was told that if the exciter winding is separate, then it would be about $1000 - cough! (he was shooting from the hip having not seen it).
Just figured I'd pass on what I'd learned.
Steve