Mine (95 Electra Glide) is about a 1/8". Talking with HD techs your Jack Shaft has a torque rating stamped on the head (mine was 120)...they said just run it in until you reach the torque rating...that did not work so well with mine.
The key is that when you push the start button that you get a good tooth alignment/mesh....not to deep and not to shallow.
Keep in mine that with the primary cover off, the jack shaft is going to bounce around a little.
DO NOT LET YOUR BIKE RUN WITHOUT PRIMARY COVER!
Good luck and happy trails,
jf
