Sparklessness was due to BROKEN CRANK. The motor still kicked over and had good compression, but the crank had one half sheared off and the stator didn't turn. By a stroke of fantastic good luck I found ANOTHER KT250, one with a decent crank and bottom end.
Mix and match, and I now have a running machine.
Getting closer- it runs and makes smoke. Once the snow melts I can ride it about and fine tune it.