Have you confirmed the throttle is working? Remove the air filter, look into the throat of the carburetor and twist the throttle. See if the throttle block is actually opening and closing. You should see about 1/2" of movement, up and down as you twist and release the throttle grip. If not, that's your problem and you need to check the cable attachment to the throttle block (squarish aluminum part that moves, or should move)I've got the exact opposite problem. My idle runs crazy. Can't even ride it, its too loud and vibrates like crazy. It is really high even if I back out that screw all the way. The cable tention doesn't seem to affect it either. Tensioned or all the way loose, its same thing. I read somewhere on this forum someone had the same problem. No idea whats happening. Also I put in the 70 jet because most people say it runs better.