I agree that you shouldn't blindly mess with the governor. Perhaps you should check the frequency of the output voltage though. If the generator is running fast, that might explain the higher than average voltage.
There are several ways to measure the frequency. Some of the better digital multiimeters can read frequency. You could use an oscilloscope if you have access to one.
Here's a down and dirty low-tech way to measure generator frequency:
If you have an old analog electric clock, you can plug it into the generator and measure its error relative to an independent and accurate time piece. (The speed of the synchronous motor in the clock is directly determined by the frequency of the applied voltage. This may even work with some digital clocks, but that can vary) The longer you run it, the more accurate you can be in calculating the error ratio. An hour is probably a good time period for decent accuracy.
Divide the displayed elapsed time of generator-powered clock by the true accurate clock elapsed time. If the result is greater than one, the generator is running fast, if the result is less than one, the generator is running slow. You can then use the ratio to calculate the frequency error. Expect some error. Plus or minus two or three hz is probably okay.
If you determine that the error is significant enough to require adjustment, you can make SMALL adjustments to the governor and retest. (Tightening the governor spring increases RPM and frequency.)
Last edited by motormonkey; 09-01-2019 at 12:21 PM.