Just a comment about running when new..... after that first tank or so, I have found that it is much better to PROPERLY adjust the needles, both of them, for the prop and plane you're using, without getting "over lean". Letting these run too rich for very long is not good on things....

Mine have been happiest when I tweaked 'em early for optimal transition, smooth idle, good top end.

Some black is expected when rich, depending on the oil, and that's been my tell tale for running rich. I use Pennzoil Air Cooled, but expect other non-synthetics would do the same.

Cleaner running is better overall, adjust to suit your preferences.