Hi
I think what you'll be up against here is worn parts, maybe just in the teleflex cable, maybe in all of the gear change parts so what you'll end up with is a compromise but as long as you can select all three years, happy days. This is what I did with my C... First put the gearbox in neutral, then remove the shield shaped cover on you engine to access the cable. Detach the cable from the mechanism inside. Set your handlebar position to approximately neutral position & reconnect the cable at the engine. You may find you have to move the cable to reconnect it. Check now if you can engage all gears. If you can great! go for a ride to make sure you really are fully in gear when selected. If not, try moving the cable a little up or down, which will obviously move the neutral make out of position but if you can get all gear its something I'm afraid you'll have to live with unless you want to hunt down new spares, only some of which are available. You may have noticed small grub screws on the gear selector box, these are stop screws to limit travel of the selector mechanism & if you decide to alter these then make sure you note their positions so you can put them back to their original positions if required. Hope all this waffle helps
Mark.