Honda 250sx flat carb and back fire

[mojorising5150]

I'm working on getting a 250sx going as a practical machine seeing as my Tri-z is on the fritz. I love it and it's fast but the reliability is a major issue, would you FLY in a Yamaha? hell no, make it a Honda. Anyway, the carb is extremely flat until it gets higher in RPMs and then it keeps reving a second or so after I let of the throttle. I have that damn choke needle hooked up and all but I'm unsure how to tune this problem. Also when it's reving down it back fires out the pipe as well as the carb. Is this valves or is it more of the same carb issue?

[Yamaha_Rules69]

It almost sounds like your rocker arm to valve clearance is too big. i would check the clearance, and if that dosnt help mess with the carb. Did you clean the carb? It may be dirty. The part where you said it revs before returning to idle makes me think your slide could be sticking, or your throttle cable could be routed incorectly, damaged,or needs to be lubed. Spray some wd-40 on the end of the cable so it gets lubed, if you think it looks like it needs lubed. Good luck and to the boards.