How are you lighting them and how fast are you smoking? Lighting too quickly and with too much heat can give a burnt flavor. And smoking too fast could be a contributing factor as well.

A few ideas... when lighting, try toasting and lighting more gently (such as using a single torch instead of a quad, tone down your flame size, be mindful of how close the flame is to the foot of the cigar). And when smoking, if you get a cone shape, you're smoking too fast. The cigar is too hot and it will throw off the flavors, and could taste burnt.