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.

Reuse the generator cover or a service cover with puller 88713.1749 fitted. Secure cover to crankcase half with some of the original screws and begin separation by turning the central pin of the tool.

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

Remove the screws (31), remove the pipes (33) and collect the O-rings (32).

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 “Overhauling the main bearings”).

When renewing the primary shaft bearings (14) and (12), install them to the crankcase half using spacers (17) and stop plate (9) and fasten with screws (18) and (8) respectively.

At each overhaul it is recommended to renew also the sealing ring (13) in-between bearing (12) and chain-side crankcase half: lubricate the ring (13) with denatured alcohol, drive it fully home against the crankcase half, and orient it as shown.

At each overhaul it is recommended to renew also the oil sealing ring (11) on the outside of bearing (10) as well as oil sealing ring (20) on the outside of bearing (21).

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. The angle-contact ball bearings are designed for bearing combined loading (radial-axial loads).

Bearings of this type can bear 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.

On badly worn engines, bearing outer rings may have developed clearance in the crankcase halves - normally, bearing outer rings are interference-fit in the casing.

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

After installing new main bearings, shim the crankshaft as described in the paragraph “Shimming the shafts” and “Reassembly of the crankcase halves “ of 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 screws (8). Fit the retaining plate (9) to the gearbox secondary shaft bearing (10) screwing the screws (8) fully into the chain-side crankcase half.

Tighten the screws (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.

Bearings do not have a specific mounting position (except main bearings); however it is good practice to install the bearings so that side bearing the writing is facing upwards.

Fit seal (28) and needle roller bearings (24), at the height indicated in figure “E”, and ensuring that the three parts are fully home one against the other.

seal (28) shall be positioned as shown in figure “F” and needle roller bearings (24) shall be mounted so that the side with “writ­ing” (G) is facing the casing.

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 ring.

Thus, we obtain:
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 thickness 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 screws in the seats indicated in the figure and tighten them to the specified torque (Sect. C 3, Engine torque settings).

Note on the dial gauge the total clearance and add a preload of (0.30 mm) plus the thickness of the shims used (1.90x2=3.8 mm).

Install the O-ring (32) on its seat (A) in the crankcase half. Fit the pipe (33) in the crankcase half, inserting the end (B) fully in the O-ring. Align the hole (C) of the pipe with the threaded hole (D) in the crankcase half. Apply threadlocker to the screw (31) and start it in the threaded hole (D). Tighten the screw to the specified torque (Sect. C 3, Engine torque settings).

If removed, apply recommended threadlocker on the dowel (30) and tighten to the specified torque (Sect. C 3, Engine torque settings).

To avoid damaging the oil sealing ring (20) on the timing belt driveshaft, protect the threaded end of the shaft with the special protective cap 88700.5749. Dampen the oil sealing ring (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.

Insert the 1st-4th and 2nd-3rd speed selector forks (B) in their respective channels in the driven gears of the secondary shaft.

Insert the 5th-6th speed selector fork (C) in the driven gear of the primary shaft.

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 half.

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.

Prepare the crankcase screws and insert them in the alternator-side crankcase half (3); note that the screws are of different lengths.

Tighten all the screws 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 you have fitted are free to rotate or move correctly.