sounds most likely a fuel problem to me. with those symptoms.
do you keep it stored indoors ????
not likely this but .you could check this anyway.
i had an older 2 stroke mower that had been kept stored outdoors for a long time. in all types of weather. eventually water had made its way into the sump of the engine. the engine would start and run for a while. at least until the spark plug got saturated with sumpwater .it just kept starting and running for a while.then would stop.
i do agree with Blumbly though. for a carbie assembly problem.
