JD A Idle srew

While trying to adjust the idle screw on my a, cause the tractor is running rough
I notice no difference while adjusting the idle screw in or out.Does this means the carburetor is plugged up some place or do I need new idle adjustment screw?

Good chance it is plugged up, but if the throttle plate is past the idle ports it will be running on the load side. Have the idle needle out about 2 turns throttle pulled back, then try turning the load needle down and see if it still runs. If not then the idle circuit is plugged up.

Mike is correct, you don't set idle needle with throttle lever at idle. At 3-400 rpm idle speed you won't see any affect by turning idle screw unless you shut it all the way. Takes very little fuel to idle at that speed. Fast idle is where you set idle screw. Use procedure he mentioned above. That's how you not only set idle mixture but trouble shoot idle circuit. Tractor sitting still, no load and throttle wide open should only use idle circuit.

What????

that's all the louder I can speak.

see if this works...Engine warm , idle needle 2 turns open and load 1 turn open , now open throttle LEVER on steering pedestal to wide open. While wide open slowly close load needle all the way. It should NOT change engine speed.( If it does then idle circuit is plugged.) Now start slowly,a few clicks at a time, turning in the idle needle until you notice the least little hesitation/roughness and quickly turn it back out 1/4-1/2 turn and leave it alone. Now idle it back down to low idle and open load needle back up one turn. To set load needle without actually hooking up to a load , throw throttle lever wide open quickly. It should speed up instantly and with a few puffs of dark smoke right at first then clear up. If it hesitates much or pops then open needle up until it does not. One to one and a half should be right there. If and when you hook to a load, then you can fine tune load right between smoke and pop but it should be close to right on already. If none of this works like I said then you have carb trouble or fuel delivery trouble or air leaking somewhere. throttle shaft and/or bushings , stripped drill plugs , rust plugged passages , plugged nozzle , plugged bowl vent or air bleeds , worn throttle blade , wrong float level , carb/manifold gasket leaks. Endless possibilities.