Bold reference numbers in this section identify parts not shown in the figures alongside the text, but which can be found in the exploded view diagram.

Re-use the alternator-side crankcase cover or a service cover with puller 88713.1749. Secure it to the crankcase half using several of the original bolts and begin to separate the crankcase halves by turning the central pin of the tool.

Remove the gearbox shafts and gearbox selector drum from the crankcase (Sect. N 7.2, Removal of the gearbox assembly).

Check that the surfaces of the crankcases are perfectly flat using a reference surface. Check that the bearings (4) and (23) are in good condition. Note that the main bearings must always be changed in pairs (refer to the procedure below in “Overhaul of the main bearings”).

After having renewed the gearbox shaft bearings (14) and (12), secure them in the crankcase with the spacers (17) and the retaining plate (9) fixed respectively with screws (18) and (8).

At each overhaul it is recommended to renew also the oil seal (13) located between the bearing (12) and the chain-side crankcase half. lubricate the oil seal with denatured alcohol and install it in the crankcase half, orienting it as shown.

At each overhaul it is recommended to renew also the oil seal (11) located outside the bearing (10) and the oil seal (20) outside of the bearing (21).

Check the condition of locating bushes (19). In the event of evident signs of distortion or excessive assembly clearance in their bores, remove the locating bushes using appropriate tools.

The main bearings have are of the angular contact type with offset inner races so that the balls transmit loads from one groove to the other along straight lines at an angle to the axis of the bearing. Angular contact bearings are designed to bear combined loads (radial and‑ thrust loading).

Bearings of this type can withstand thrust loads in one direction only. In fact, under the action of a radial load inside the bearing, an axial force is created that must be counterbalanced by an axial force acting in the opposite direction; that is why these bearings are generally fitted back to back in pairs.

Check that the interference fit between the crankcase and the installed bearings (4) and (23) is not less than 0.03 mm, otherwise the crankcase halves must be renewed.

After installing new main bearings, shim the crankshaft as described in the paragraph “Shimming the shafts” and “Reassembly of the crankcase halves” in this section.

The crankcase halves must be in good condition and perfectly clean. The mating surfaces must be perfectly flat and free from burrs.

Apply threadlocker to the bolts (8). Fit the retaining plate (9) to the gearbox output shaft bearing (10) screwing the bolts (8) fully into the chain-side crankcase half.

Tighten the bolts (8) to the specified torque (Sect. C 3, Engine torque settings).

The ball bearing (7) with circlip (6), in correspondence with the timing belt driveshaft, oriented so that the closed side of the plastic roller cage faces the crankcase half.

None of the bearings except the main bearings have an obligatory assembly direction: it is good practice to install the bearings so that side with the writing is facing upwards.

Before assembling the crankcase halves, calculate the shims required to obtain the correct end float of the crankshaft and gearbox shafts.

measure the depths “LA1” and “LA2” corresponding to the distance between contact surface of the crankcase half and the contact surface of the inner race of the bearings.

Add a preload of 0.30 mm to help seat the axial load crankshaft bearings correctly, then insert the inner race in the outer race.

This gives:
SA=LA1+LA2+0.30-LA.

SA=SA1+SA2
where “SA1” and “SA2” represent the shims for the clutch-side crankcase half 1 and the alternator-side crankcase half 2.

In addition to the above procedure, the following is a practical shimming method, providing a guide on how to calculate the crankshaft shim thicknesses accurately.

Install a shim (A) of minimum thickness (1.90 mm) on each side of the crankshaft to prevent contact between the crankshaft web and the engine block.

Fit four M8 bolts into the holes shown in the figure and tighten to the specified torque (Sect. C 3, Engine torque settings).

Note the dial gauge reading. This is the crankshaft endfloat. Add a preload of (0.30 mm) plus the thickness of the shims used (1.90x2=3.8 mm).

If removed, apply the recommended threadlocker to the grub screw (24) and tighten it to the specified torque (Sect. C 3, Engine torque settings).

To avoid damaging the oil seal (20) on the timing belt driveshaft, protect the threaded end of the shaft with the special protective cap 88700.5749. Dampen the oil seal (20) with alcohol and fit it on the timing belt driveshaft, seating it against the roller bearing (21).

When refitting used components, before installing the gearbox assembly in the crankcase half, make sure that the inner races (A) of the gearbox shaft bearings are fitted into the correct bearings and have not been left on the shafts.

Install the selector forks of the 1st-4th and 2nd-3rd gears (B) in their respective grooves in the output shaft driven gears.

Install the 5th-6th gear selector fork (C) in the input shaft driven gear.

Fit the shimmed crankshaft into the clutch-side crankcase half, positioning the connecting rods (E) in correspondence with the relative cylinder barrel seats.

Make sure that the connecting rods (E) are correctly positioned in the respective cylinder seats. Incorrect positioning of the connecting rods at this stage will inevitably lead to the need to re-open the crankcase.

Apply a uniform and continuous bead of DUCATI liquid gasket to the mating surfaces of the crankcase halves, going around all the holes as shown in the figure.

Tighten all the bolts to the specified torque (Sect. C 3, Engine torque settings).

Check that the crankshaft can be turned with a certain amount of interference with the main bearings (the crankshaft should have a pre-load of 0.15 to 0.20 mm); check also that all the parts fitted are free to rotate or move correctly.