[jkv45]

What TJ said ^, and what does the inside of the tank look like?

Have you checked the condition of the air filter lately?

There could be debris from the tank that has made its way down to the carbs and is holding a float up (dumping extra gas in and maybe out the overflow) or the fuel pick-up screen or filter (if there is one on that Gen) may be getting partially plugged.

With that many miles there could be a number of things that need attention, like the plugs if they haven't been changed recently.