You need a bushing of some sort.....it supports and centers the input shaft.
If there is a bushing in the center of the crankshaft (as opposed to a little roller bearing) just wipe off the inner face and put a light coat of grease in it.....also a light coat of grease on the input shaft nose and splines.
Light means, coat using your finger tip....almost transparent...as opposed to blobs that'll get thrown at the disc, (and create engagement shudder).
If there is a formal roller bearing, remove it, replace with new, and put a fair amount of grease in it if not prepacked with lube.
Rob