I'd get that head gasket checked out. Before he gives up might as well pull the head off. Broken rings I don't believe would smoke lightly, compression would be an issue as well as power and your oil consumption would go up. Is this one of the Kohlers with or without the adjustable valves? Whats the oil level like? Full, burning oil? What color is the smoke? Head gaskets aren't that bad to change, a little more work than on the briggs, but not terrible.
Also, you can grab a craftsman or scotts with one of these engines used fairly cheap, they are good engines, run quiet
Also, you can grab a craftsman or scotts with one of these engines used fairly cheap, they are good engines, run quiet