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 forksRemoval of the cylinder heads
Using the tool code 88713.2676, Undo the nuts (21) on the cylinder head stud
bolts.
Remove the cylinder head nuts (21) and special washers (22).
Remove the cylinder head assembly by lifting it off the engine studs.
Repeat the same procedure for the other cylinder head. ...
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 ...
Refitting the steering head components
Important
The steering tube bearings (6) are identical but in no case may their
components be swapped around during reassembly.
Clean all contact surfaces and lubricate with the recommended grease.
To fit the external rings (c) of the bearings (6) to the steering tube, use the
tool with par ...