So, from my meanderings here on AdvRider, I've deduced the "Hurricane Mod" simply converts the petcock to manual operation (both a vacuum operated petcock and a manual petcock are "gravity" type feeds) and the "22 cent mod" is just as simple, shimming the carb needle, right?
A question or two then, and a bit of general input.
The question is who comes up with these silly names for the "mods" Why can't it simply be called "shimming the needle" and so forth?
The input would be that adding 30cc of displacement shouldn't really change the jetting much. Since the butterfly in the carb isn't the real limiting factor in the airflow, but really the slide which is lifted (pushed up, actually) by the difference in air pressure between atmospheric and the lower pressure of the venturi, 30cc shouldn't make enough of a difference in the jetting.
If you're having to keep the enrichner open slightly to keep it running right though, it's either the idle jet is slightly plugged (not likely) or you do need a bigger idle jet. If your air filter was clogged, the bike would run richer. If you've got a leak between the filter and the carb, it'll run leaner. As the engine spins up and the main jet/needle jet take over, the fuel metering is more affected by the slide position, and the idle jet, while still flowing fuel and affecting the mix, doesn't really do a lot.
And to further confuse things, a new engine will change it's fuel requirements as it breaks in.