My small one is 10 years old and still starts on the second pull m once a month
What engine? My generac 5500 (?) has some "chinese honda copy" 390cc OHV
and that would start knocking with a PCMO oil when hot.
You both need to adjust valves on your generator(s)....
Valves get tighter when hot and no loss of power so ... why Mr. K ?
I did have to adjust the valves on my new Toro 252cc snowthrower after about only 10 hours.
The ex. valve lash measured only 0.10mm
and it should be 0.20mm ( 0.0008") !
I knew it needed something as The engine was spitting and popping when hot, had very loud exhaust and lost power