This is the deal with the CNS carb. It's actually a better, more sophisticated carb than a NT or Speed carb, but possibly because of new EPA laws that went into effect this year, or maybe even total ignorance on the part of the factory, the carb comes out of the box jetted so lean a 80 won't even run. A 48 might run a little better but probably not much.
Then to really confuse the issue, the actual size of the main jet isn't that much different from the size jet found in a NT carb, but that doesn't mean much because the CNS is a different animal.
I'm pretty sure that the reason it runs so lean with the same size jet is because the CNS has a two fuel circuits, instead of the NT's one. On the CNS, one air bleed is feeding two circuits, instead of the NT's one circuit. The pilot and the main. The NT just has a main.
Usually motors that come with a NT carb have to be leaned it out from the factory setting, especially if it's a 48cc.
This is my opinion of what's going on. Because the pilot jet relieves some of the pressure on the main circuit, the main doesn't suck as hard as on a NT carb. That's the reason you have to have a much bigger main jet than a NT has in order to compensate for the reduced suck. This means the same things we do to get a NT carb to work better won't work on a CNS carb.
In the end you get the same amount of gas, but the CNS is more precise over a wider rpm range.
My question is, does it come from the factory jetted so lean it won't run, because EPA laws force the factory to do so, or is it because the factory is so stupid they though the same size jet would be Ok?
