Here are someother questions to help out others to answer yours. Does it accelerate and then sound as though it bogs down then die? Or is it when you just mash the throttle then die? Does it idle fine? Does it take off quick or studder a bit then die? And last, how are your temps when this happens or how long has the engine been running when it happens? Helping diagnose an engine is hard to do online but with all the right info we can usually pull together and get you in the ballpark of running right.