2 year old Northern lights with 61.7 hertz under load

It s a little high if under a full load. What do you get lightly loaded? Won’t really hurt anything though.

Your old 120Vac clocks may run faster.
62 htz will not hurt anything.
It's just a minor/micro governor adjustment.
With a good freq meter you can do it your self but at 62 htz, not a worry.

Remember, at 1000 hours you have a cold valve adjustment. Order your new spaghetti top valve cover gasket and air filter.
Have a quality htz meter and adjust all then.
Usually at the first 1000 hours I really rinse the sump and if not already using it, change to Shell T5 10w40.
New belt, eye ball the raw pump real well.
Back flush the H E.
Dip the coolant and adjust coolant supplement. Fix all leaks.

It's all in the manual.