one needs a proper governor, for maintaining the engine speed,
most use some type of mechanical governor,
the governor on my generator is the same that is used on a combine harvester of the same era as the engine manufacture,
(in my opinion having some extra engine is not a problem), as the surges do not effect the seed droop as much and the recovery of the speed,
the droop should should be less than 5% which works out to about 2 cycles, for most situations,
normally my generator keeps with in about 1% in the cycles,
for a poor mans cycle meter,
one can take a old plug in clock with a second hand, and then time it with a digital or battery unit, the longer you time say 5 Min's vs 1 min, the more accuracy your reading will be,
I usually set my generator up to about 61 to 62 with no load and when it starts to load it will set in to about 60 cycles a min,
but try to keep it in the 55 to 65 cycles out put, other wise you will stress the electrical equipment you have,
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if the engine does not have a built in governor like a tractor or combine or small engine, one will need some type of exterior governor added on to control the engine speed,