The number one Generator Maintenance Tip is:
You gotta run the generator.
Just letting them sit for months or years at a time will guarantee it will not start when you need it.
At least every couple of months run your generator for an hour or so. Best to also actually use it to run something while you are performing this maintenance tip. You know, like your AC or some other appliance.
If your generator has an electric start, it also has a battery. This battery must be kept charged. So, you run the generator. This is to charge the battery for the electric start. If you don’t run the generator often enough it won’t start when you need it. How do I know this? From experience… the best teacher.