well what motor you have doesn't matter. however if your seeing a peice of anything in there that is blocking it thats your problem. but if your turn the spring in your hand and hold the screw so it doesn't turn it should thread off so you could then thread the idle screw in. just to see of the threads are ok. you must use the spring otherwise the vibration during it running will move your idle screw, thus messing up your tuning of the motor. if you have some motor spray or starting fluid, which is and has been what i use for six years to clean all my cars, electric or nitro, anyways use it to spray out your carb area and thus the metal you see in the threads. but when you do this it will move that metal inside of the carb and then the motor. so it would be best to remove the carb from the motor to do this.
if you look around your motor where the carb fits in it, you wil see a nut that crimps the carb into the motor. this nut will be between the carb and the cyclinder head. loosen it but not all the way off. then wiggle your carb until it slips out of the motor. now then you can spray it out with wd-40, motor spray, or starting fluid as these three products will not hurt anything. then once you se any debris is gone, try to thread the new idle screw in. if at this point you still have trouble you will need a new carb body.
try this and see if it helps you. and if not let me know and we'll go to another fix.