SInce it's fairly new keep it running rich. Don't start trying to really lean it out until you have 15-20 tanks through it. OS engines are great and run almost right out of the box, but you still need to "baby" them a bit while they finish breaking-in. Keep it rich so that you see a smoke trail when running and you'll be fine. Once you get to about 15 tanks then start leaning it out a bit at a time. You may have to readjust the low end as well.

Ken