Jeff,
Hopefully, the problem will turn out to be the ratchet gear on the rear end of the layshaft jamming on the bronze bush and staying out of mesh. A more serious option is that the auxiliary shaft has broken out of it's end support.
In any case, the first thing you need to do is remove the final drive from the gearbox. You will then be able to look inside the tail end of the 'box and see what is happening when you operate the kickstart. As you look into the 'box, you will see the final drive bevel gear on the main shaft, immediately below that is the tail end of the layshaft with the kickstart ratchet on it. The ratchet gear has a light spring keeping it in mesh - the gear should be free enough to slide on the bronze bush. Overtightening the layshaft nut sometimes causes the bronze bush to bulge so that the gear will not slide.
If all is OK here, look even lower in the 'box and you will see a short auxiliary shaft (in line with the bike) - this should be supported by the small round plate in the rear end of the gearbox - these shafts have been known to break out of the rear support. Unfortunately, when this happens, it often damages the front support as well (and that is part of the main case).
When you have identified the problem, get back to me and I will try to assist with a remedy.
Regards,
Eddie.