Was this somewhere else on the site? This is the easiest and most concise explanation to understand for a FNG.First the venturi always works. This isn't a 4 barrel carb waiting for the secondaries to kick in. Don't even bother to think about it operation like that. The transition your (most likely) reducing to is the engine getting on the pipe, or possibly transitioning to the main jet. Its not really difficult to set the jets. Low is arguably easiest. Get the engine warmed up, turn either direction and listen for a rich bog then lean rpm pickup. Go right in the middle between those 2 points. Start running it looking for transition, should be crisp not bog. Don't get the carb low to high jet transition confused with getting on the pipe, that's 2 different things. Then go about tuning the top end. It's a hearing thing for me, get the most rpm without breaking up then enrich the high needle a tad for a little safty margin. You should recheck the low jet. There is a little over lap between the two jets. You shouldn't have to be constantly changing the tune, unless there's a major temp swing, fuel/oil ratio change, elevation etc.