Generator Timer Click, click how to change

Considering no body know what generator we're talking about it's hard to make a good recommendation. However, it is almost assuredly not 120v.
Most Onan and other quality generators use a 12v meter. Many portable types wrap the spark plug wire as bgum mentions.

It is my understanding that the timer runs by wrapping a single wire around your spark plug wire. That should give you a good idea of the voltage. Check YouTube for how it works.