If it starts runs then dies, that is a huge clue towards fuel flow issues, and the in-tank filter ( if fitted) or the feed from the tank being a restriction, best to take the tank off, blow out the fuel lines to the carb. Blow back the tank outlet and reflush the tank with fresh petrol.
I had to do, as above, on one that get used infrequently, the fuel in the carb bowl was like jelly, the needle and seat needed a good polish with very fine waterpaper rolled into a thin "cigarette" and spin in the seat holder, its seat and inlet then blown out completely with a good blast of compressed air, the fuel line blown backwards and forwards, the glass bowl feed blown through from both sides and the (possibly not originally standard) small stainless steel ultra fine mesh between tank and glass bowl receiver.
Tank flushed, then the outlet blown out, (cloth over the normal fuel filling inlet and a good gulp of breath blowing that way, then compressed air the other way through the small outlet followed by a further tank flush.
This may sound like I'm beating an issue to death, but I captured all the old fuel in a clear plastic 2 ltr cooldrink bottle and left it overnight to settle out... ouch! .....will use the old fuel for cleaning stuff.
What a difference free flowing, and plentiful, fuel makes, love the smell of clean fuel in the morning ! then reset carb setting for smooth idle and medium revs running
A freshly cleaned and polished plug also plays a stunning role too.
[if it were running, but flooding, great clouds of dark fumes, coughing, belching, smoky run would be indicated plus fuel dripping from air filter are symptoms]
