welcome to the forum! If the idle mixture screws don't seem to make any changes then the reason could be that someone previously may have installed incorrect parts like the springs on the needles. whatever the case it may be preventing the needle from doing their job. what year is the M4ME. Newer carbs have metric threads that are very fine thread and require alot of adjusting to do anything [sometimes]. Try and see if the needle is actually seating. If the spring bottoms out before the the needle seats then that will prevent the needles from doing their job. As stated in other posts, sometime you may need to trim the spring a little if the idle hole have been drilled out or sometimes you may have to go to the old style of needles which requires some machine work. If none of that works then your fuel supply is coming from somewhere else during idle. you should have at least some kind of control of the idle with the adjusting screws. Good luck.
