That really is an excellent article.Mind if I stick my nose in again? The NT carb. used to be the go to engine up-grade. Lots of tuning info..
Bicycle engine tuning - Ultimate guide to NT carburetor tuning (power-bicycle.com)
okay i tried both and it runs good and its fast without the airfilter and a lot less bogging downA good test to see where your jetting is, is to remove the air filter & ride the bike at full speed...
If it runs better (without a filter), that means the jet is too big... If it runs worse, that means the jet is too small.
Please try this test & report back.