Originally Posted by Panhead
While doing a bit of cruising on the ol' soldier I made the amazing discovery that leaving just a bit of the choke closed on that nice, new carb seemed to make it a bit more eager to run. This makes me think there's some experimentation ahead. Of course, this may be due to the drilling I've just done on my exhaust, too. I think that engine is just now turning enough miles to be beginning to be broken in - sorry I never kept track of just how many.
I've always found that the engine begins to run leaner as the rings seat. Most like to be set leaner at first, but can be richened a bit later. Whenever I deliver a new engine without running it in well myself, I always send it out a bit on the rich side to allow for this.