I'm assuming (perhaps incorrectly) that you are going to purchase one of SBP 4-stroke shift kits to use as the base for your set-up? I'm also assuming that you are wanting to use #41 chain (1/2" pitch)? Dax offers a 10t PTO driver (power take off) that fits the output shaft of the 3.25:1 reduction box. So using the calulator 10 in the first field and 32.5 in the second field gives you 3.25:1. then the output of the box is a 10t then 10 again in the third field which will drive a 17t driven on the left side of the jackshaft, so 17 into the forth field, this equals 1.70:1 reduction. The right side of the jackshaft has a 9t driver on it so 9 goes into the fifth field and the driven sprocket on your crankset is a 48t so 48 goes into the sixth field. this equals 5.33:1, for a over all reduction of 29.47:1 before you factor in your multi speed freewheel/cassette. I ran some #'s using the 36t to an 11-34 rear cogstack and think that the ratios might be a bit on the high side. You would probably find that using a 30t on the front chainrings to be a more suitable range. If you want to run the #'s your self just input 10 into the first field and then 294.7 into the second to get your 29.47:1 reduction then you can input any combination of front chain rings 30t, 36t into the third field and any # of cog sizes from 11t - 34t into the forth field. Leave the fifth and sixth fields at 1.
ocscully