Just bought a basket case 1980 XS400 SG. Electronic ignition. PO was attempting to make it into a cafe racer. . I've completely rewired it using the original harness and EVERYTHING works.....except.....when turning it over on the starter motor, I get just ONE spark on the right plug only, and then nothing. Pause and hit the starter button again, and the same thing. One spark, then nix. Tried all the usual. Replaced coils, leads and plugs with items I know are good. Battery was fully charged overnight. Any thoughts?