mike : Your comment about switching from a 12 to an 8 in the Carb . Being out of Rotax a few years , I was planning on buying a weather station and getting the proper software to determine the best jetting . Should I be holding out on that or will the Proper software have to be re-configured . ?
Bob, most all jetting software has a means of calibrating the software a small percentage for your specific carb/engine combo. So in the beginning you need to experiment a wee bit and dial the software in. But then it becomes pretty much enter the weather data and go with few exceptions.
None of the software I’m aware of have the venturi as a spec. Most all do have float weight/idle jet & emulsion tube size/needle type/spark plug/and float arm height.