So I stand corrected. I just took mine apart. The nut pushes on the sprocket, the sprocket pushes on a 0.005 shim, the shim pushes on the spacer, the spacer pushes on the bearing and the bearing pushes back on the face of the drive gear. So the total width of the bearing, spacer, shim and sprocket is too wide on yours or something is in the way.

Dana