Replace any damaged gears or gears with excessively worn dogs or dog holes.

Shift Fork Guide Pin/Drum Groove Wear InspectionOxygen Sensor Installation (Equipped Models)
NOTICE
Never drop the oxygen sensor [A] especially on a
hard surface. Such a shock to the unit can damage
it. Do not touch the sensing part [B] to prevent oil
contact. Oil contamination from hands can reduce
sensor performance.
Tighten:
Torque - Oxygen Sensor: 25 N·m (2.5 kgf·m, 18 ...
Oil Seal, Grease Seal
Do not remove pressed oil or grease seals unless removal
is necessary. Replace with new ones whenever removed.
Press new oil seals with manufacture and size marks facing
out. Make sure the seal is aligned properly when installing.
Apply specified grease to the lip of seal before installing ...
Drive Chain Lubrication Condition Inspection
If a special lubricant is not available, a heavy oil such as
SAE 90 is preferred to a lighter oil because it will stay on
the chain longer and provide better lubrication.
If the chain appears especially dirty, clean it before lubrication.
NOTICE
The O-rings between the side plates seal ...