i hope this might help.......if the shifter is on a spline remove it and adjust it according to your foot hieght......i went and looked at my 748 and if i had to adjust mine then that is what i would have to do......good luck.
If you look at your linkage you'll see a turnbuckle and two threaded ball joints with locknuts at the adjusting rod (middle section of the linkage between the nuts). The fwd locknut is left hand thread and the rear is standard. Loosen both nuts then turn the adjusting rod to lengthen or shorten the linkage to raise or lower the shift lever. If you can't get the lever to the right position with just the barrel adjustment. Then move the shift arm (the one that clamps to the transmission shaft) one or two spline teeth to get the corse position then fine tune it with the adjusting rod. Make sure you leave enough threads from the ball joint inside the rod to insure that it's solid when you tighten up the lock nuts after you get the shift lever to the right spot. I think you should be able to get it with just the rod and the lock nuts if it's just a boot adjustment. Try that first before moving the splines. Your owners manual should have some diagrams and info on adjusting the bike to you.