An expensive lesson

European (and especially Italian) motorcycles are much like a high-maintenance girlfriend, they don't tolerate neglect and if you're foolhardy enough to neglect her needs she WILL make you pay.
In all seriousness, European motorcycles are very expensive to own and maintain, with Ducati and BMW heading the list.  Many prospective and first-time Ducati owners are shocked to realize that they will be facing maintenance costs of 600-1200 dollars (depending upon exactly what is needed and who does the work) EVERY 6500-7500 miles. This maintenance simply can not be deferred as these bikes will not suffer neglect the way that some other bikes can.  It is simply the cost of owning an exotic vehicle and something to keep in mind if you're contemplating the purchase of a bike like this.

Here we have a 2003 Ducati 999 Monoposto, looking very seductive in her bright yellow dress and carbon fibre jewelry.  Hot, yes?  It has 13,000 miles and is due for its second major service.  Apparently the starter clutch started playing up and rather than getting it taken care of immediately, the owner put it off until the sprag failed completely.  The extent of the damage is detailed below.

Here is the alternator cover ready to be removed.

Once the flywheel was removed, here is what was found.

After cleaning everything, the full extent of the damage becomes apparent as the gear and the outer race are also destroyed.

Here is the new starter gear, compare to the failed gear in the second photo.  Yes, much of the metal that used to be that gear ended up in the oil.

Here is the new sprag and flange ready to be assembled to the flywheel.

Here I will show just how easy it is to screw things up if you aren't careful during assembly of the flywheel/sprag/gear assembly.  In these photos only the bearing and spacer are shown for clarity.
There is a thrust washer that goes between the crankshaft timing gear and the starter gear.  The inner bearing collar MUST pass THROUGH the thrust washer when assembled, as shown in this photo.

When it is correctly assembled on the crankshaft, it will look like this.

If the thrust washer slips off during assembly, this is what will happen.  Note that the washer is off-center and is trapped between the bearing collar and the crank gear.  If the flywheel nut is tightened with this condition present the thrust washer WILL FRACTURE and also relieve the torque on the flywheel nut, causing much damage.

The correct way to reassemble the assembly is this, use some grease to hold the thrust washer in place and rotate the starter idler gear while sliding the assembly onto the crankshaft splines.

Speaking of splines, you can't just slap the flywheel onto the crank any old way.  The oil hole in the flywheel must be aligned with the large groove in the crank.

The last step before closing up is to reinstall the alternator rotor.  Contrary to what the manual says, the rotor bolts must be replaced.  The updated bolts are class 10.9 whereas the old-style bolts are class 8.8.  There is a considerable difference in strength.  They also should be thoroughly degreased and Loctited and torqued to proper spec.  I assemble the rotor to the flywheel with the flywheel installed because it's easier than doing it on the bench.  The stock flywheel nut is only temporarily holding the flywheel.  The final assembly is with Nichols double nuts, Loctited and torqued to 140 lb. ft.

 I will not go into replacing the belts, etc in this post as that procedure has been detailed elsewhere in this blog.

One final note: 
There is a lot of talk on forums about shortening the sprag spring or replacing it with the spring from some seal or other, in order to prolong the life of the sprag.  This is nothing less than butchery.  If you can't afford the parts, maybe you shouldn't own a Ducati.  If you take the bike down this far and don't do the job right, maybe you shouldn't own tools.