For all those that run 15-20 minutes and then stop:
Disconnect the gas line from the main tank at your generator fuel pump.
Connect a new shorter line to the pump and drop into a gas can on the ground.
Restart it and see if it will run for a long period, like an hour or more.
This test will tell you if you have fuel line leaking air coming from the main tank.
I chased the problem for a couple of months during hot weather thinking it was vapor locking, bad fuel pump, clogged filter, etc...
Never had another issue after replacing the complete fuel line.
