What year machine is it? I have a 2012 that I had to have the entire barrel replaced under factory warranty.It started to come unwound and shorting out as well as the shunt coils being too large, which reduced the air gap to an almost non-existent amount; in turn restricting air flow through the generator barrel, thus keeping it cool.  With the machine running, you should be able to feel a significant amount of air blowing out of the vents of the barrel behind the engine. If you don't, then chances are that you've got a blockage between the coils.
It seems that all the engine drives from Lincoln are now produced in Canada. Their quality standards do not seem to be nearly as good as of years past in my opinion.
These machines production were put on an indefinite hold.
In regard to turning down his rpm... that is what the idle control knob is actually doing for him now. It is an 150 RPM swing down from high idle. 10 on the dial being set at factory high idle. Mine is quite touchy... just moving it a fraction of one digit seems to change the way it welds a fair amount.
I would have it checked by a qualified welder mechanic if not done so already. They should be able to megger the generator to check for voltage leakage from the coils to ground.