Nephew's '80 G3 Sachs has no fire at plug. Blue lead from magneto to positive side of coil shows no voltage on multi-meter when cranking, , verified no ground on blue lead from kill switch or harness. Points at .016, does read resistance in coil negative to positive. What should I see on meter on blue lead from magneto when unplugged from harness? Looks like yellow from magneto is for head/tail-light, blue/black for stop stops, blue for ignition only. What resistance should be seen on positive coil (with and with-out plug grounded)?