don

Sounds like maybe it is getting flooded... or maybe starved... Try pulling the plug and letting it air out and see if that helps. At the same time check to see if the plug is wet with gas.

Also have a look at all the parts along the fuel line, especially the float bowl. make sure there are no cracks and that everything is working ok. I had a cracked float bowl once that would draw enough suction to get gas from the tank, get the engine started, and run, but then it leaked so bad it did not run very well....