After a short hiatus away I got back to the '78 with the left carb issue (another thread). Carbs are now thoroughly clean, with new (standard size) jets, new OEM needle jets & O-ring and needles. I had been chasing a super-rich condition on the left side that just carboned the left plug badly. I temporarily utilized the nice running '77D model carbs to assure myself it was carb related. Those plugs read a nice light tan after a 30 mile run. Put the now-clean '78E carbs on, and the pic shows the difference. As suggested, I am too lean, running with 4" (lightly oiled) UNI filters and some kind of aftermarket mufflers.
What to do, what to do? Should I throw the stock airboxes from the '77 (with K&N filters in them) and take that for the same run again for comparison? Or raise the needle a notch? Both? New larger jets? I think 5twins put up a nice carb differences sheet I need to go find again and read that once more.
Pic is of the plugs. Left is left.