Just an update.
After re-assembling the engine, the putting the contactless ignition on i found it still ran backwards.
Then I realised that it seems to run backwards at a perfect 22 degrees just as forwards. I find that the rotor trigger has two magnets at around 45 degrees! Obviously when kickback occurs, the other magnet allows it to run backwards. For now I replaced with contact breakers and it has fixed the problem seemingly. It does kick back, but it doesn’t ‘support itself’ and continue to run in reverse.
I guess case closed.