you could try what Kaw rider suggested. The only problem is it may shift fine while "bench testing" but as soon as you put a real load on it - nothing or the sound of grinding nuts and bolts. If there is a problem trying to shift while "bench testing" then the problem could be withing the cases. I am currently in the middle of a tranny issue that I put on the back burner untill winter. My tranny shifts fine while spinning the countershaft and or by spinning the clutch as Kaw rider stated, but as soon as you fire it up and try to go for a spin, its like false neutral with a nuts and bolts jumbling around sound....I have identified my tranny problem thru trial and error and lots of discussion on this site. Your situation could be different than mine, but I would inspect clutch and components, and even replace ( its gonna wear and need replacement anyways) then test ride.
That way you could eliminate that possible cause and move on to the more labor intensive tranny inspection and fix.
BTW - your last post described exactly what my bike did the first time the clutched was burnt.
good luck - keep us posted
