7.2 - | Gearbox assembly: gearbox shafts

1 | Shim, thickness 1

2 | Gearbox input shaft

3 | Shim, thickness 0.5

4 | Needle roller bearing

5 | 5 th speed driving gear

6 | Splined washer, thickness 0.5

7 | Circlip

8 | 3 rd- 4th speed driving gear

9 | 6 th speed driving gear

10 | 2 nd speed driving gear

11 | Shim, thickness 1.8

12 | Splined washer, thickness 0.5

13 | Selector drum

14 | Special needle roller (square cross-section)

15 | Shim

16 | Selector drum assembly

17 | Needle roller bearing

18 | 1 st speed driven gear

19 | Shim, thickness 1

20 | 5 th speed driven gear

21 | 4 th speed driven gear

22 | 3 rd speed driven gear

23 | 6 th speed driven gear

24 | 2 nd speed driven gear

25 | Gearbox output shaft

26 | Shim

27 | Shim, thickness 1

28 | 1 st, 4th- 2nd, 3rd speed selector fork

29 | 5 th, 6th speed selector fork

30 | Selector fork shaft

31 | Shim, thickness 1

32 | Needle roller retaining circlip (square cross-section)

Parts catalogue

Gearchange CONTROL
Gearbox

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

Operation | Section reference
Separation of the crankcase halves | N 9.2, Separation of the crankcase halves

Withdraw the selector fork shafts (30).
Move the forks (28) and (29) to disengage them from the slots in the selector drum (13).
Withdraw the selector drum (13) taking care not to lose shims (31) and (27) mounted on the shaft. Note that the positions of the shims must not be inverted.
Now you can renew the needle roller retaining ring (32) and the special needle rollers (14).
Remove gear selector forks (29) and (28).
Remove the gearbox input (2) and output (25) shafts complete with gears, taking care to recover the spacers on the ends of the shafts.
If the bearing inner races (A) are left on the shafts, slide them off the ends of the gearbox input (2) and output (25) shafts (Sect. N 9.2, Overhaul of the main bearings).
After removing them from the shafts, install them in the respective outer bearings in the engine crankcase half.
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 output shaft
Remove the chain-side shim (15) and clutch-side shim (26) from the output 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 output shaft (25).
Disassembly of the gearbox input shaft
Remove the chain-side shim (11) and the clutch-side shim (1) from the input 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 input 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 endfloat by shimming the gearbox shafts and the selector drum with suitable shims.
For the total gearbox shaft and selector drum end float values, refer to Sect. C 1.1, Gearbox.
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 renew the gear or the fork by referring to the limits specified for each part (Sect. C 1.1, Gearbox).
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 renewed by comparing these dimensions with those of new components (Sect. C 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 input shaft (2), with the calculated end shims (1) and (11) (Sect. N 9.2, Shimming the shafts).
Figure 2 shows all the parts to be reassembled on the gearbox output shaft (25), with calculated end shims (15) and (26) (Sect. N 9.2, Shimming the shafts).
Reassemble the gears on the gearbox shafts by reversing the disassembly procedure.
Take particular care when installing the idler gears. The assembly of the 3 rd and 4th speed gears and the relative fixing components on the output 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 3 rd speed gear (22).
Fit 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 4 th speed gear (21).
Fit another 3-pointed washer (6) and another circlip (7) onto the shaft Seat the circlip using the drift used previously.
Reassembly of the gearbox
To reassemble the gearbox components follow the procedure under Sect. N 9.2 relating to “Reassembly of the crankcase halves”.
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.

Operation | Section reference
Reassemble the engine crankcase halves | N 9.2, Reassembly of the crankcase halves