1. Clutch drum/Primary drive gears; 2. Inner ring; 3. Inner bearing; 4. Spacer; 5. Threaded ringnut; 6. Lock washer
Caution! 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.
Removal of the primary drive gears
| Operation | Section reference |
| Drain the engine oil | Changing the engine oil and filter cartridge |
| Remove the clutch-side crankcase cover | Removal of the clutch-side crankcase cover |
| Remove the clutch assembly | Removal of the APTC clutch |
| Remove the oil pump | Removal of the oil pump |
Withdraw the clutch drum (1) complete with roller bearings (3) and the driven gear of the primary gear pair (A).
Remove the circlip (2) and the internal spacer (4).
Straighten out the lock washer (6) on the nut (5) securing the primary driving gear (B).
Restrain the primary driving gear (B) using service wrench no. 88713.2423 and unscrew the threaded nut (5) securing the pinion.
Remove the nut (5) and lockwasher (6).
Remove the primary driving gear (B) using puller 88713.2092 and interposing a packing piece of aluminium or copper between the crankshaft and the screw of the puller.
Take care to recover the key (C) from the crankshaft and the internal spacer.
Refitting the primary drive gears and checking backlash
Fully degrease the crankshaft splined end and the corresponding spline on the primary drive gear.
Check that the key (C) and internal spacer (D) are in position on the crankshaft.
Fit the driving gear (B) onto the crankshaft with the oil pump drive sprocket facing the crankcase.
Temporarily secure the gear with the washer (6) and nut (5).
Caution! If fitting a new primary driving gear (B), check the backlash.
To check the gear backlash, temporarily fit the clutch drum (1) complete with internal spacer (4), driven gear (A), roller bearing (3) and internal bush (2) on the gearbox input shaft. Fix a dial gauge to the engine crankcase, positioning the stylus against a gear tooth.
Turn the driven gear (A) to mesh the teeth and check with the dial tool that backlash ranges between 0.05 and 0.07 mm.
Repeat the check at 16 different points of the driven gear.
If the measured values are outside the permissible tolerance limits, try changing the position of driven gear (A) on the input shaft, leaving the driving gear (B) on the crankshaft. If the backlash is still outside the tolerance limits, renew the primary drive gear pair (1).
After checking the backlash, restrain the driving gear (B) with service wrench no. 88713.2423 and tighten the nut (5) to the specified torque (Engine torque settings).
Stake the lock washer (6) onto the nut (5).
Refit the oil pump and check the backlash between the oil pump gear and primary drive gear on the crankshaft (Refitting the oil pump).
Thoroughly degrease the mating surfaces of the clutch drum (1), the internal bearing (3) and the bush (2).
Fit the internal spacer (4) to the input shaft with its flat side facing outwards. Install the inner bush (2) and clutch drum (1) with driven gear (A) complete with roller bearing (3).
| Operation | Section reference |
| Refit the complete clutch assembly | Refitting the APTC clutch |
| Refit the clutch-side crankcase cover | Refitting the clutch-side crankcase cover |
| Refill the engine with oil | Changing the engine oil and filter cartridge |