Sounds like the carb is in need of cleaning/adjustment.
Bear in mind that my knowledge of carburettors could fit into a box of matches, without taking the matches out first.... so caveat emptor!
So... if it won't run with any throttle, I'd guess that the main jet is blocked. It'll start and just about run on the idle jet, but as soon as you feed it more air, it's not getting enough fuel, so it dies.