Does the new one look the same as these two, and is this different than your original? First picture is existing original '73 Supersport, and second is new replacement- appear the same. Both my 1973 and 1974 250 SS came with a 6V battery setup.
I'm guessing with your magneto, there's no battery, correct? Could this possibly be a significant spec difference between 250 Sport Special vs 250 Supersport models?