stumble

Hi All, After getting spark on this bike it started and idles well. It now has another issue. It wont rev up and stumbles and backfires at mid to high rpm. When this happens it smokes out of the carb and stalls. Included is a video of the bike doing this. The carb has been gone through and is...

I have something to ask.The bike starts alright and runs good but from right above idle the bike surges or hesitates just a little{that is the bike in gear pulling out or piddling around}.Feels like a lean spot.The bike revs through this and runs great otherwise.Should I lower the clip on the...