[asphaltgambler]

.........I'd like to add a few thoughts.

1) Regarding ignition timing with dual plug HD's - that generally you can back off total timing 2 -3 degrees and make the same power. Also if you increase cranking compression you need less total timing as well. But to dial it in - the engine needs to loaded on a dyno and the AFR already dialed in.

2) HD's are under-squared engine designs - not big news. What is news though is the air flow requirements for a long stroke set-up. Add compression, increased cam timing and port flow and those air flow numbers (requirements) go up substantially. In order to properly load the cylinders with adequate fuel the fuel 'map' looks like the side of a mountain.

As in: from start to rpm limit the amount of fuel needed cannot be supplied from a standard 2-speed fuel jet circuit carb. Further, there may need to be air correction jet(s) either changed or added where there was a fixed jet prior.

While the Mikuni is a good carb (as well as a few others including stock CV) there is a real solution. Zipper's Performance ( Jessup Maryland) sells / modifies S&S carbs. They add a 3rd fuel circuit that atomized for top end fuel supply. Now you can tailor the fuel curve with 3 circuits ( sometimes a 4th ) tuning your main jet for midrange and using their patented Thunderjet for 4200+ RPMs.

Also, depending on your combination - they will add air correction jets and or bore the venturi and extend the main jet emulsion tube up into the air flow. In the end - the fuel loading the cylinders will match the airflow requirements of the engine through-out the RPM range.