I took the right and left crankcase covers off to check the one way bearings and replaced gaskets/ cleaned out the oil filter screen. After reinstalling the covers I attempted to shift the transmission out of neutral to check the function, but I cant get it to go into 1st gear or neutral.

Where do I begin to troubleshoot this thing? I turned the engine over and rotated the output shaft while attempting to shift but the lever stops before clicking into gear. everything turns freely.