thanks so much but I did check the same connections as in your photos and they looked as new. Also I had the ign sw apart last summer (no use since then other than the aborted test ride) and the terminals all looked fine. I DO have 13.75 v where the Yellow& White (also Blue and White) wires come back to the seat area from the kill switch after going from batt to ZD to ign sw to kill switch.
Thanks to you after about 180 hours spent I now have spark during cranking (and kicking, and under compression) by following your and Stuart's advice. I installed a 7.5 amp fuse en route.   However weirdly after I disconnected the batt to solder in after mocking up, when i reconn the batt the dash lights lit up. (Current going in reverse?) Not knowing what to do I turned the ign ON and then OFF and that seemed to reset it and its normal again. I have now removed the batt for winter storage so expect the same weird result in Spring when I reconnect. Is this harmful?  Any thoughts on issues A and C?