I see you have no responses so far......so lets try helping:
Starts OK and runs 5 seconds, then dies......sounds like it ran out of fuel as a first WAG. I assume you primed it first? Does it start OK on a second try and do you have to re-prime it again? Possibly a failing fuel pump or plugged fuel filter? You could try to remove the fuel line after the pump and crank starter to see what kind of fuel flow you get into a bucket. The other thing is check your oil level in case you are equipped with low oil shutoff.
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