I don't have a built in generator on my 5er, but I've had a stand alone generator for over 15 years. I try to run it monthly as it primarily used for power outages at the house. However, there has been many times when I've got for several months between start ups and it's always run very well. It almost always starts the 2nd or 3rd pull of the cord.
I keep Sta-Bill in the gasoline fuel tank and when shutting down, I always turn the petcock to the off position and let the carburetor run dry and the engine shuts itself off.
When starting it back up, after sitting a month, or two, or three, I simply flip the gas flow valve again, wait about 5 minutes, put it on choke and about 2 pulls of the rope, it starts.
The only exception is when the temperatures are zero degrees, which has happened in the winter months in the past. Then, I had to pull, and pull, and pull, but eventually it would start.
We have 2 garages, the big one not attached to the house and not heated where the trucks are kept, the other a one car garage attached to the house I use for a wood working shop. The last couple winters, I've been storing the generator inside the smaller heated attached garage. When we had a power failure last winter, the generator started right up. So, it's now permanently stored in the smaller garage attached to the house, as it's always slightly heated and the generator will still start easily, even if it's zero degrees outside.
This is my experience with my generator. But from my limited experience, I wouldn't stress leaving the generator unattended to for 3 months.
