If your idle screws are all the way in then you have issues elsewhere not the ignition.
+1
If the bike runs and you are getting good spark, then you need to consider looking at the fuel delivery. A properly tuned bike should not idle at all with the idle screws turned all the way in. Working on carbs sucks, and denial ain't just a river in Egypt. I once swapped engines because of a poor running condition since I did not want to open up the carbs
yet again. The donor engine, with the same carbs, ran exactly like the one I pulled out. At that point I had to overcome my denial and was resigned to addressing the carbs. The fact that the idle screws are turned all the way in, yet you are still experiencing an overly rich condition, leads to several possibilities:
>Vacuum leaks
>Float heights
>Jet sizes
>Idle stop screw set too high
>Loose/broken/sticking carb components
>Any combination of the above
If you have a stock ignition, then by all means install it just to rule out any issues with the aftermarket ignition. The idea is not to change too many things at once until you have resolved the problem, or you will never know what the problem was. Worse yet, by making too many changes at once, you can inadvertently fix the original problem, yet "break" something else that exhibits the exact same symptoms!
I hate it when that happens...