91 cr 125 wont idle

on my 91 cr 125 i cant seem to get the bike to idle. i have had problems with this bike since i have owned it, it always seems to run really bad until 1/4 throttle. anyway, my service manual say they air screw should be turned out 2 turns but the bike will not idle at 2 turns at all, but it doesnt run bad to 1/4 throttle any more, i have to turn the air screw
countless times before it will idle but the then the bike runs horrible again until you get past 1/4 throttle then its runs fine. do you think that
i have a bad choke? the air screw control from idle to 1/4 throttle right? like i said at 2 turn with the air screw the bike runs good but doesnt idle, but when i turn the air screw until the bike idles the bike run horrible until you get past 1/4 throttle then its fine.

i know that is how you set the idle but i have to turn the knob so much to get it to idle and when i finally does idle it runs awful until you get past 1/4 throttle. when i have the screw set on 2 turns it doesnt idle, you have to keep it running but the problem at 1/4 throttle is gone.