Quad is hard to shift. Especially when its running. Much easier to shift when it not running. Seems like high is the worst. Any ideas??

Check your belt and clutch alignment.

Pull cover, work belt off, wash out clutches with brake cleaner, blow out really well, install a new belt, and replace cover. Should shift like new.

If it still feels kinda sticky, remove the bell crank and spray in some lithium grease to free up shifter movement.