Honestly, it would have to be looked at.. first i'd check the cheaper parts ie the linkage... check if you have any loose bolts, make sure the cables aren't stretched, or that the linking parts missing... both sides, the trany and shifter side.
then after that is checked out and you drive around a bit with some fresh oil in the trany then see if its still hapening, i'd disconect the calbes on the trany side and try shifting then, if its tough still then check the shifter side see if there is something getting in the way.... then move the cables alone by hand... hows it then.. after all that is checked out good i'd say then go into the engine bay and try shifting each rail by hand and see how it feels.. maybe the fork is stretched out or just needs to be oiled up..
I know that side to side move was really really tough... front to back wasn't soo hard.. but still hard...
-E
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