Interesting issue.. I recently came across an 03' R50 that you could not move the gear shifter past the centre line to the left. So basically with the shift lever vertical it will move freely forward and back also goes the right then forward and back no issues. No detent felt for 5th or reverse. If you try to move the selector to the left off centreline it moves dead straight and smoothly. Removed the cables off the transmission issue still present. Cables move smoothy and appear in good condition. Any thoughts before I pull the lower cover off the gear selector tomorrow?

 

Found the issue. Cable sheathing had pulled out of the end at the transmission effectively making reducing the amount of travel the cable could produce. This was the left hand cable. Hope this helps someone in the same boat.