Yamaha YZF-R125 Service Manual: Lubricating the drive chain
The drive chain consists of many interacting parts. If the drive chain is not maintained properly, it will wear out quickly. Therefore, the drive chain should be serviced, especially when the vehicle is used in dusty areas.
This vehicle has a drive chain with small rubber O-rings between each side plate. Steam cleaning, high-pressure washing, certain solvents, and the use of a coarse brush can damage these O-rings. Therefore, use only kerosene to clean the drive chain. Wipe the drive chain dry and thoroughly lubricate it with engine oil or chain lubricant that is suitable for O-ring chains.
Do not use any other lubricants on the drive
chain since they may contain solvents that could
damage the O-rings. 
Adjusting the drive chain slack
NOTE:
The drive chain slack must be checked at the
tightest point on the chain.
CAUTION:A drive chain that is too tight will
overload
the engine and other vital parts, and one that
...
Checking and adjusting the steering head
1. Stand the vehicle on a level surface
WARNINGSecurely support the vehicle so that there
is
no danger of it falling over.
NOTE:
Place the vehicle on a suitable stand so that the ...
Other materials:
Intake air temperature sensor
1. Check:
Intake air temperature sensor resistance
Out of specification Replace
the throttle
body.
a. Connect the pocket tester ( ×
1k) to the
throttle body sensor assembly coupler as
shown.
Positive tester probe
brown/white "1"
Negative tester probe
gray/black ...
Checking the tires
The following procedure applies to both of the
tires.
1. Check:
Tire pressure
Out of specification Regulate.
WARNING
The tire pressure should only be checked
and regulated when the tire temperature
equals the ambient air temperature.
The tire pressure must be adjuste ...
Checking the friction plates
The following procedure applies to all of the friction
plates.
1. Check:
Friction plate
Damage/wear Replace the
friction plates
as a set.
2. Measure:
Friction plate thickness
Out of specification Replace
the friction
plates as a set.
NOTE:
Measure the friction plate ...