your stated that it was running fine until you tried to adjust the idle.........I cant think of any reason why adjusting the idle would make it misfire...might make it run bad if you adjusted in down to much..
are you also adjusting the carb ??
if it was running good till this point I dont know of anything that would change it..
how high was the idle when you try to adjust it.. I always ran mine a little on the high side..
let us know when you find the problem,
and if you get it running good again, dont mess with the idle.......lol