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:
Bearings and oil seals
Install bearings "1" and oil seals "2" so that the
manufacturer's marks or numbers are visible.
When installing oil seals "1", lubricate the oil seal
lips with a light coat of lithium-soap-based
grease. Oil bearings liberally when installing, if
appropriate.
CAUTION:Do not spin th ...
Checking the ignition coil
1. Check:
Primary coil resistance
Out of specification Replace.
a. Disconnect the ignition coil connectors from
the ignition coil terminals.
b. Connect the pocket tester ( × 1)
to the ignition
coil as shown.
Positive tester probe
red/white "1"
Negative tester probe
orange ...
Checking the brake fluid level
1. Stand the vehicle on a level surface.
NOTE:
Place the vehicle on a suitable stand.
Make sure the vehicle is upright.
2. Check:
Brake fluid level
Below the minimum level mark "a" → Add the
recommended brake fluid to the proper level.
A. Front brake
B. Rear brake
WA ...