This article is from the Ducatis Motorcycles FAQ, by Duke Robillard firstname.lastname@example.org with numerous contributions by others.
You may just need the Ducati factory clutch update -- a factory upgrade to
the clutch pack for all '91 and '92 dry clutch machines that was made
standard on the '93s. The update kit is amusing: it's one plate, a special
slightly convex one, and instructions on how to reorder the plates in the
clutch pack. You take one out, you shuffle the deck and viola! smoother,
quieter engagement is supposed to result.
The '91 and '92 904cc motors were equipped with a clutch which had flat
pressure plates, dual sided friction plates, one convex pressure plate and
one specially thick, single sided friction plate. Somewhere around late '92
or early '93, Ducati revised the clutch pack. The revision is to toss the
thick friction plate, add another convex pressure plate, and shuffle the
pack a little bit. This upgraded clutch pack is a warranty/ upgrade item
and should be available free of charge from your dealer to my knowledge.
The new pack is installed thus:
(cover side > engine side)
Pp - Fr - Fl - Fr - Sp> - Fr - Fl - ... - Fr - <Sp - Fr - Fl - Fl - Ba
Pp - Pressure Plate
Fr - dual sided friction plate
Fl - Flat pressure plate
Ba - clutch basket/hub
Sp - convex or spring pressure plate. These plates are distinguishable by a
single dot on one of the spline tangs, on one side only. The directional
arrow ("Sp>" or "<Sp") indicates which direction the dot should face.
... - continue alternating however many Fr and Fl plates in between.