Hope someone can help motor ran fine last fall, now I only have spark at two of the three cylinders , tried different (used) coils . Didnt help? Not sure what to try next..
If changing coil's didn't help, assuming the used coils were good, it is most likely the power pack. There is a remote chance that the timer base is bad, but it dosen't happen often. There are voltage checks for pack and timer base output, but you need a special voltmeter.