It ispossible you could have bad or dirty float or needle and seat. Do you notice gas dripping on the ground when idling, or enrichment valve sticking open. Also you can try Four new plugs. See my most recent post about an issue I had. The plugs in it were new but it took four more new plugs (same make and type) to cure issue. Last if your valve clearance is too tight, the valves may not fully seat when the engine is real hot.