Welcome to the site !!
When you say the shift forks "look good" did you actually check them with the specs in the manual ??? , a fork can be bent and not "look" bent , as well as the shift shaft(where the shifter attaches) can get bent in a fall , and bind up ..... BUT , I am assuming the bike was apart when you got it ?? , if so , are you sure the shims are in the correct location and the gear shafts are not pushed to one side of the case or the other because too many shims are on one side , and not enough on the other ???
There can be a number of parts that can cause binding , including on the clutch side where the shifter detent cog and spring is , right down to the shifter shaft , not counting the gear parts ...... if you are certain that the shims are in the correct locations , and have measured the shift forks for deformities , then look into the shifter shaft (going from the shifter to the clutch side) , and make sure it is not bent from a impact ......other than that , generally , when shifting is hard in places or in general , it is usually a shift fork , or possibly the shift drum , but I would think you would see obvious signs of wear on the drum ....