[Cal Metal]

Bob Putnam has some good advice here. Check the timing/valve lash, etc. Also, the suggestion regarding a linkage check is a good one. Often times these carbs are blamed for things for which they are not responsible. It would seem peculiar to me that the carbs would be running good one day and poorly the next.

Spitting and popping back through the carb is a sure sign of a synchronization problem. This doesn't appear to be the case here. If you tend to peter out at top end--everything other part of the range being good--your air correction jet is too big, braking the mixture flow and over emulsifying (lean).