RE: Strimmer Engine CDI conversion,which Spark Plug
sparking at the sensor means the plug cap wasn't grounded properly, this will fry the sensor after a few seconds and then no more spark...
by default i think most of these ignitions come with a cap designed for the CM-6 unless you specify otherwise. if you tried to use this kind of cap with an RDJ8J (5/8" hex taper seat) it would fit on and make contact at the top of the plug just fine but would not ground against the base of the plug like it should.....look at the various sites selling ignition and parts to see how these caps should fit. and if this is indeed what happened then you should probably be OK if you get the correct plug cap kit and a new hall sensor.