My guess is that it was probably flooded or fuel fowled. It is way more volatile than gasoline. And it's so "hot" that if you use too much (or on a hot engine, especially a diesel), you risk over revving or pre-ignition.
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So, you haven't tried it since this problem started?
Another option: When it dies, quickly pull a few of the easy to get at plug wires, connect some spare plugs, ground them, give it a spin and take a look. (Exhaustive go to ;-)