So a couple of videos, the first showing it running flat out with about 80% choke, then the effect of removing choke, shown at the carb, where it starts stumbling and dies. The second is it starting at idle with no choke, then trying to gradually introduce revs.
Full revs to no choke:
https://youtube.com/shorts/qQAejaOIz8E?feature=share
No choke idle to revs:
https://youtube.com/shorts/mOj3QcGQN7k?feature=share
Poorly video'd on my phone so apologies for sound...
Had ocnfirmed by another this evening that it was running OK only a year ago, so I'm struggling to make the jump to a mechanical issue. I'm just bolting and unbolting the carb, will take the shroud off tomorrow and have a clean, is there potential for a vaccuum leak further in than the manifold / carb mating surface?