Somehweere, Axial bought several .28RRs from the factory with lemon carbs. It was hit or miss, you could have gotten a great running RR or one with a horible carb that would not keep from running away no matter how rich you set teh needles. STS had a similar problem. Air leaks are what we are talking about. These are from improper machining at the factory, and no tuning can correct them. You could turn the needls out so rich that they just about fall out, but the engine will still run away from massive air leaks.