spark plugs can foul way down inside and still look fine. Pull the spark plug, hook up the ignition wire, ground the plug against the engine. Spin the engine and see if the electrode sparks.

Had an old D-17 AC tractor did same thing. Tried everything even blowing air thru fuel line into tank. Would run a few minutes and die. Fugured out rust in fuel tank and after it run a few minutes the rust would block line again . Pullrd trank off and put some rocks in it and shook fire out of it. Run good after that.

It it were mine I would try to see whether the sparkplug was wet or dry inside right after engine stopped. Wet - indicate ignition problem. Dry - indicate fuel problem.

Very nice and succinct trouble-shoot. Show a pic of the plug
after it was running if ya can Just. Im betting water in fuel. Fought it
with my sled.

Drain all fuel and lines.
If you cant, try a fuel additive starting with a K...like K100 or something like that.
In a red bottle.
That stuff is great, mixes with water to fire a plug.
Im betting it was stored outside, water pooled on the tank (which takes up
the whole top of said generator) and leached in through the vented cap.
Water in fuel, especially if it runs for a bit then quits.
Check plugs after that, youll see oiled up moisture on them.
Theyll run for a bit after the plugs get cleaned, but will keep pulling
moisture from the fuel to the plug and therefore cutting off the motor.
And...old plugs lose amperage to fire those plugs as hot as they should be firing.

Got it running
Changed oil and new spark plug.
Old oil came out like syrup. Blacker than the dark side of the moon.
Guess the plug was the problem.
I've never had a plug I couldn't clean well enough that the engine wouldn't run.
Thanks for the help guys.
just

I work on small equipment on a regular basis. I have run into fairly new plugs which wouldn't spark correctly. New plug, and it runs like new. Might have something to do with modern gas formula.

I have a Subaru 3000 psi pressure washer with a similar engine. Runs great and strong. When I bought it, Lowe’s had a special on Honda pressure washers and I went to get one. The manager showed one in inventory but it was gone. He offered me the more expensive Subaru for the same price. I really only wanted Honda, but I gave in. Can’t say enough good things about that engine. Works great.