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.

After removing the oil sealing ring (2), tap from the inside towards the exterior using part of the inner race of bearing (4) to be removed, after moving aside spacer (5) located between the two bearings.

Once disturbed, the oil sealing ring (2), circlip (9) and the spacer (5) must be renewed. The latter two components must always be renewed as a pair.

Remove the oil pump (Sect. N 2.1, Removal of the oil pump) in order to be able to disengage the driving gear (D).

Install the tool 88713.0137 on the gear (D) and hold it against rotation by inserting a pin in one of the engine mounting bolt holes.

Remove the primary driving gear (D) using puller 88713.2092 and interposing a packing piece of aluminium or copper between the crankshaft and the screw of the puller.

Temporarily fit the gear (C) complete with the bearings and the oil sealing ring onto the gearbox primary shaft and fix a dial gauge on the crankcase; position the dial gauge stylus on a gear tooth.

Turn the driven gear (D) to mesh the teeth and check with the dial tool that backlash ranges between 0.05 and 0.07 mm.

Measure the backlash at 16 diametrically opposed points of the gear.

If the measured values are outside the permissible tolerance, change the position of the driven gear (C) on the primary shaft leav­ing crankcase gear (D) untouched. If still outside tolerance values, renew the primary drive gear pair.

Install the tool 88713.0137 on the gear (D) and hold it against rotation by inserting a pin in one of the engine mounting bolt holes.

Tighten the nut to the specified torque with a torque wrench (Sect. C 3, Engine torque settings), turning clockwise.

Refit the oil pump and check the clearance between the oil pump gear and primary drive gear on the crankshaft (Sect. N 2.1, Refitting the oil pump).