The hard starting problem you have may be caused by slack in the choke cable. My V12 had a start problem which I traced to the cable to the carbs. This resulted in only a small choke action. Get someone to pull the choke out while you watch the carb linkage. If you can lift the choke lever further when the cockpit choke is all the way out, that is the problem. Adjustment is easy as all you need to do is loosen the screw holding the cable at the carbs and pull on the wire to remove the slack then tighten the screw. Hope it works for you!