Hi Steve
Had similar problems with my Transmission build it shifted fine without the weight of the gear shafts sitting on the forks, but when the gear shafts were installed over the forks it didn't seem to be shifting thru all the gears. The way I checked to make sure it was shifting thru all the gears was bolted the cases togeather and shifted it to neutral then put a dot of white-out on the drum where it comes thru the right side and was able to see the dot rotating for each gear change.