Small Engines (Lawn Mowers, etc.): Yamaha YG6600DEY Generator

Question
Good Afternoon. MY generator will not stay running.(low hours and maintained) It will start up, fine run well for a few minutes then start to run a little rough then stall. it may even backfire through the muffler. If you try to restart immediately it will backfire loudly through the muffler. If you wait a minute or so it will start right up and run for another minute or two. It will not stay running if you spray carb cleaner in carb or loosen fuel cap. I replaced float needle, removed and thoroughly cleaned the carb and fuel tank and fuel valve. Checked spark while running, looks little weak (not sure) but never stops. Removed fuel solenoid and plugged carb. Still shuts down after a minute or 2. Have not checked valves and cannot locate low oil switch or wire to isolate. Did not check keyway.

Answer
Even with low hours I would still check the valves.  It is possible the ignition is faulty but it's difficult to troubleshoot.

It is possible you have an air leak, somewhere in the intake system.  When the engine starts to warm up the parts will expand, a little, and it could be a slightly warped intake isolator or gasket.  Did you remove the carb from the engine when you cleaned it?  I am assuming you did but just want to verify...let me know.

Eric