Check all of your linkages for funky bends, adjustments etc. Best to get the FAM and service manuals for details.
Also, open up the little linkage box and see what treasures are there. Mine had some worn shim pieces that were jamming up the works. Clean out, inspect and adjust, and re-lube. The forks can get worn, and might be spent, or welded and reshaped if you can.
Also, you can 't shift it like a modern tranny. Push the lever straight up out of third with an open hand, without pulling front or back and let it slip into neutral. Double clutch and go to your next gear. And just enjoy the whole experience!.
