Small Engine Troubleshooting Problems? Ask a Mechanic Now.
What is the model number of the genset?
There can be several things that can cause this: engine running too fast, bad voltage regulator or controller (depending on what model it is), damaged stator etc.
Test the frequency. It should be set to about 62 Hz, with no load on the genset.
If the frequency is good, the voltage regulator is bad and will need to be replaced.