You explain that when the ped died the first time, a new plug would show a good spark until you installed it, then get wet and quit sparking. This was almost certainly too rich. 2 cycles can foul a plug faster than you can change it when they are too rich. The second time it died, you mention that the plug was a nice grey color. Was it wet and did you then have the same symptoms you had after the first failure?
I think Fred is on the right track. If you have dirt traveling through the carb, when it sticks to the needle valve you run rich and if it travels to the main jet you run lean or stop.
Keep us posted,