Starter idler gear in single shear

The stock 1098R intermediate starter gear is held in place with a long screw (12) which holds the gear “pin” (8) in the engine case in single shear.

Since the starter motor gear and sprag clutch gear are not all in alignment with this idler bushing, it causes a (pulsing) lateral force on the bushing which eventually ovals out the case hole where it mounts. This in turn causes the idler gear to misalign & grind against the cases shedding aluminum into the oil.

The next step in this happy process is the idler screw snaps off.

Then it's time to pull the left sidecover and the flywheel (with the flywheel puller). If you're lucky, like I was, you can get the remainder of the idler screw out with some needle nose pliers. If you're not so lucky, it's ez-out time.

Fortunately, Ducati figured out this is a problem and updated the starter idler gear mounting design.

The updated stator cover (13) found on the 848evo, 1198sp (and possibly some other models) has an outboard support of the intermediate starter gear bushing.

Solution

The other problem is the intermediate gear (10 in the 1098R diagram) is at too high of a ratio and puts undue stress on the starter and gear.

So the updated intermediate gear has 11 teeth instead of 13, which turns the motor over a little quicker.

Idler gear ratio

You didn’t come this far to stop