How old is the motorhome and generator? This is a classic symptom of a failing fuel line from the main tank. I had the same issue on a 10 year old coach with an Onan 5500 here in Fort Worth. And older fuel line will develop small cracks and suck air (sometimes).
Mine would run great in cooler weather but had the same symptoms in the high heat. Thought it might be vapor locking but after replacing the entire line from the main tank to the generator fuel pump it has never died again. Need to also look at the line from the fuel pump to the carb.
Hope this helps.
Michael