93 535 IGNTION MYSTERY

i have no spark on the rear cylinder, both coils and pickup coil are working.the flywheel only has 1 magnet (is this correct?) i dont understand how a single pickup coil and a single flywheel magnet can fire two cylinders 75 degrees apart.i have tried several igniton boxes (all used,yuck) with the same results. this bike was bought used and its past is a complete mystery, it has not run yet. If i swap the spark coil pigtails
i get a spark on the other cylinder so i know the coils and wires are o.k.  I've double checked all the wiring
and it seems perfect,as are resistance readings at the coils, and the supply voltage.