Thanks Bob. Hoping I eliminated the chances of #3 with the new regulator.

Wayne Presley also suggested the possibility that it may be running too rich. I did have a base tune put on it, and I see a good A/F ratio at idle, but haven't tracked it during go-karting under load at slightly higher RPMs. Will go-kart this week again with computer connected and data logging and then look through the logs.

Keep the suggestions coming. I'd like to move on to body fitment with any open mechanical issues lingering!