Removed the Geni today for a full service. Any tips?

You can buy an electric (110VAC) hour meter, that will only run, when the genset is running and generating power. They aren't to expensive. I know they have them at Grainger's, but I'd guess that most lawn Equipment shops would have them too, for the riding mowers, though that one is usually mounted with the spark-plug, not the output of the genset.