I got my son an 08 crf 50, and put an fmf exhaust on it and it ran just fine, and last week i put a free flowing air filter on the carb, and now it seems to be starving for fuel, even when pinned.. from idle, which is set a bit high to keep it running, to full throttle, it bogs and sometimes pops is this a lack of fuel issue, or too much airflow? when reving it, you can hear the carb gulping air, is this too much for a termite bike? I run k&n aircleaners on my Busa's and GSXR 750, but never seem to bother it any.. PLEASE HELP.

 

You need a bigger main jet. Dont quote me on this but I think if you go up two you should be fine. I would get a few different sizes though just to be safe. They are cheap enough.

 

Yes it's too lean now. Any mod to airbox/cleaner almost always needs a re-jet. As stated, a couple of sizes main jet should fix this problem.