If its the cylinder that does not fire that has low compression then prob need a new tip end. My bike was not firing on one cylinder but when i had my buddy switch the throttle cable he had a little mix up with the carb cap with an extra set laying around the shop. The needle was a notch or two higher and was washing out the spark......but yea if you pick it up i would start with the carbs and spark. Its only three key factors with a two stroke.