80cc 2 stroke wont reach full rpm

[Jayraye39]

I just got done with a project wit a new engine kit and the bike fires right up and run great intill I hit 18 mph then starts four stroking. I've check for air leaks there is none and played with the jetting and put a different cdi box on it. seems like no matter what I do it's still four strokes the only thing I changed was the intake and like I said I have no air leaks could my intake be to long? I'll include a photo. Any suggestions is greatly appreciated. Thanks

I would toss that carb as they are very hard to adjust for the average joe. The JRL BoFeng carb is a much better option and simple to adjust. It is more than adequate to run on a 10mph to 50 mph motor. More than half of the members in here have the BoFeng installed