Don't tighten it down hard or you will damage the spring. Just tighten until you feel it stop, then back it off and see how it does. Would be useful to count the turns until it stops, then you know how for not to back it out. :)
Screw it all the way in gently and count the turns, then back it off by half the turns and see what it does. Been a while since I messed with a two speed, but once you find the spot to change it, it takes very little one way or the other usually to change it, like 1/4 turn one way or the other...