I had an Honda XR-600 motorcycle that wouldnt fire for shiz.I remember wiping the flywheel and stator clean (CDI ignition) and dang thing fired right up.After replacing the (expensive) stator, no more problems.I'm with you it's probably the coil... And a gas engine needs spark, compression, fuel/air, and timing. Since the flywheel is fine the timing is controlled by the coil anyway. Only other thing would be a bad plug especially if its the resistor type. Sometimes if you squish the gap down to 15 thou or so it will spark under compression even if its a weak coil. Either way I think you are spot on and I have seen saws run with really low compression before just gutless as hell.