no spark in start

I can't know exactly where your current loss is. I know some of it is inherent. OEM wiring was barely adequate for the OEM equipment. Later models with upgraded OEM equipment have upgrades in their wiring, ign' switch, etc. Anyway...
A relay would cure it. Ign.1 and ign.2, the brown and blue, tied together would do nothing more than signal/close the relay. Added wire with fusible link from starter relay stud routed to and through the relay when its closed to feed ignition system, charging system, electric choke if present, maybe even electric fuel pump on same relay. Common bosch relay is rated at 30 amps.