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

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 - 1.1, Gearbox.
Disassembly of the gearbox shafts
Inspection of the gear selector forksReassembly of the control unit
Insert the control unit (4) into the protecting sheath (5) and position it on
the airbox.
Position the relay supporting bracket (2) by starting and tightening the
screws (1) to a torque of 6 nm +/- 10% (sect. 3 -
3, Frame torque settings), and connect the control unit connectors (3).
...
Steering head: front fork
Screw
Screw
Steering head
Bottom yoke
Left fork leg assembly
Right fork leg assembly
Counter nut
Damper assembly
Bush
Spring
Preload tube
Collar
Washer
Top cap assembly
Screw
Washer
Adjuster screw
Special washer
Fork tube + calliper unit
Dust cap
Sealin ...
Refitting the exhaust system
Refit the heat guard on the manifold (10) by tightening the nuts (9) to a
torque of 10 nm +/- 10% (sect. 3 - 3, Frame
torque settings).
Position the vertical exhaust manifold (22) on the vertical cylinder head
with the gasket (23).
Tighten the fixing nuts (21) to a torque of 10 nm +/- 1 ...