Having the same dieing issue with my 21 5 port, have about 4 tanks through it and have not got even 1 minute without dieing. Factory plug went weak, not burnt out so I put a 97T plug in and its running, but I think this carb is so touchy, it is gonna be a pain to get tuned. Have tried to follow the settings list on 453 and I'm getting there I think, but dang! Very frustrating. I actually have one of the Econo Nova's (Novarossi N21BF Limited Edition .21 )on the way, because I'm not sure I can trust this thing. Sounds real heathy when its running, but so far, cant keep it this way. Wish one of you Go Guru's lived in the KC area!!