IMO it's fueling.
What I'd do is replace the carb with a cheapy from eBay, a Kehin copy. Search for PWK Carb. They are about £20. I used one on my Matchless and it was great. I'd also fit an iridium spark plug as it's a stroker. https://www.ebay.co.uk/itm/403045437621?hash=item5dd76150b5:g:T~gAAOSwOjJhC62T