7.2 -
1
2
3
4
5
5th speed driving gear
6
7
8
3rd- 4th speed driving gear
9
6th speed driving gear
10
2nd speed driving gear
11
12
13
14
15
16
17
18
1st speed driven gear
19
20
5th speed driven gear
21
4th speed driven gear
22
3rd speed driven gear
23
6th speed driven gear
24
2nd speed driven gear
25
26
27
28
1st, 4th- 2nd, 3rd speed selector fork
29
5th, 6th speed selector fork
30
31
32
Spare parts catalogue
Important
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 gearbox assembly
 
Remove the alternator-side crankcase cover and the alternator assembly
Withdraw the selector fork shafts (30).
Move the forks (28) and (29) to disengage them from the slots in the selector drum (34).
Withdraw the selector drum (16) taking care not to lose shims (31) and (27) mounted on the shaft. Note that the positions of the shims must not be inverted.
Once removed, it is possible to replace the special rollers (13).
Remove gear selector forks (29) and (28).
Remove the gearbox primary (2) and secondary (25) shafts complete with gears, taking care to recover the spacers on the ends of the shafts.
If the bearing inner rings (A) are left on the shafts, slide them off the ends of the gearbox primary (2) and secondary (25) shafts (Sect. 9 - 9.2, Separation of the crankcase halves).
Disassembly of the gearbox shafts
Place the shaft in a vice in such a way as to facilitate the disassembly operations.
Important
Take care not to invert the positions of the shims on reassembly:
this would potentially lead to jamming when using the gear selector control, making it necessary to reopen the engine crankcase.
Disassembly of the gearbox secondary shaft
Remove the chain-side shim washer (26) and clutch-side shim washer (15) from the secondary shaft.
Withdraw the first speed driven gear (18) with the roller cage (17) and the shim (19).
Remove the fifth speed driven gear (20).
Use two flat blade screwdrivers to remove the circlip (7) taking care not to damage the shaft surface.
Remove the circlip (7) and the splined washer (6).
Withdraw the fourth speed driven gear (21) with the roller cage (4) and splined washer (12).
Remove the third speed driven gear (22) with the roller cage (4) and the splined washer (6).
Remove the circlip (7) and remove the sixth speed driven gear (23).
Remove the circlip (7) and withdraw the splined washer (6) and the second speed driven gear (24).
Withdraw the roller cage (4) and the shim (3). All the components have thus been removed from gearbox secondary shaft (25).
Disassembly of the gearbox primary shaft
Remove the chain-side shim washer (11) and the clutch-side shim washer (1) from the primary shaft.
Remove the second speed driving gear (10). Use two screwdrivers to prise out the circlip (7) and the splined washer (6).
Important
Take care to avoid damaging the surface of the shaft while removing circlip (7).
Remove the sixth speed driving gear (9) with its roller cage (4). Remove the splined washer (6) and the circlip (7).
Withdraw the third and fourth speed driving gear (8).
Remove the circlip (7) and the splined washer (6).
Remove the fifth speed driving gear (5) with the roller cage (4).
Slide the shim (3) off the primary shaft (2).
Overhaul of the gearbox
Check the condition of the front coupling dogs of the gears. They must be in perfect condition and with no sign of wear on the edges of the teeth.
The idler gears must rotate freely on their shafts.
When refitting, make sure the circlips are correctly positioned.
Check the needle roller bearings for wear.
The threads and splines of the shafts must be in perfect condition.
Also check that the component parts of the gear selector mechanism are in good condition.
Engage the gears and check that the gearchange mechanism does not stick (selector fork - gear groove, and fork pin - desmo­dromic drum groove) due to incorrect end float. Restore the correct end float by shimming the gearbox shafts and the selector drum with suitable shims.
For the total gearbox shaft and selector drum end clearance values, refer to Sect. 3 - 1.1Gearbox.
Inspection of the gear selector forks
Visually inspect the gear selector forks. Bent forks must be renewed as they may lead to difficulties in gear changing or may suddenly disengage when under load.
Use a feeler gauge to check the clearance of each fork in its gear groove.
If the service limit has been exceeded, check whether or not it is necessary to replace the gear or the fork by referring to the limits specified for each part (Sect. 3 - 1.1Gearbox).
Inspection of the gear selector drum
Use a gauge to measure the clearance between fork pin and the slot on the selector drum.
If the service limit is exceeded, determine which part must be replaced by comparing these dimensions with those of new com­ponents (Sect. 3 - 1.1, Gearbox).
Also check the wear on the drum support pins; these must not show any signs of scoring, burrs, or deformation.
Turn the drum in the crankcase to establish the extent of radial play. If play is excessive, change whichever part is most worn.
Reassembly of the gearbox shafts
Figure 1 shows all the parts to be reassembled on the gearbox primary shaft (2), with the calculated end shims (1) and (11) (Sec. 9 - 9.2, Reassembly of the crankcase halves).
Figure 2 shows all the parts to be installed on the gearbox secondary shaft (25), with calculated end shims (15) and (26) (Sec. 9 - 9.2, Reassembly of the crankcase halves).
Reassemble the gears on the gearbox shafts by reversing the disassembly procedure.
Take particular care when installing the idler gears. The assembly of the 3rd and 4th speed gears and the relative fixing compo­nents on the secondary shaft is given as an example.
Fit the circlip (7), checking that it is fully inserted into its groove on the shaft. Push the circlip into position with a suitable size tubular drift.
Slide the washer with three internal points (6) over the shaft until it locates against the circlip you have just fitted.
To fit the needle roller cage (4) onto the shaft, first lubricate it with plenty of grease (of recommended type) and then open it slightly to make it easier to slide on to the shaft.
Fit the 3rd speed gear (22).
Fit on the gear the three-pointed washer (12), which can be distinguished from its counterpart (6) by its bigger outside diameter.
Fit another needle roller cage (4) using the method already described.
Fit the 4th speed gear (21).
Fit another safety washer (6) and another circlip (7) into the shaft. Push it inside its seat using the previously used pad.
Reassembly of the gearbox
To refit the gearbox components follow the procedure under Sect. 9 - 9.2, Reassembly of the crankcase halves, relating to reas­sembly of the engine crankcase.
As a final practical test, ensure that with the gearbox in neutral the front coupling dogs (A) of sliding gears (B) are equidistant on both sides with respect to the corresponding coupling dogs on the fixed gears (C).
Check also that there is always a small amount of clearance between fork (D) and relative groove (E) on sliding gear (B) when engaging the gears.
 
 
1