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:
Checking the starter motor
1. Check:
Commutator
Dirt Clean with 600 grit
sandpaper.
2. Measure:
Commutator diameter "a"
Out of specification Replace
the starter
motor.
3. Measure:
Mica undercut "a"
Out of specification Scrape
the mica to the
proper measurement with a hacksaw blade
...
Installing the valves
The following procedure applies to all of the
valves and related components.
1. Deburr:
Valve stem end
(with an oil stone)
2. Lubricate:
Valve stem "1"
Valve stem seal "2"
(with the recommended lubricant)
3. Install:
Lower spring seat "1"
Valve stem seal "2"
V ...
Removing the front wheel (disc)
1. Stand the vehicle on a level surface.
WARNINGSecurely support the vehicle so that there
is
no danger of it falling over.
2. Elevate:
Front wheel
NOTE:
Place the vehicle on a suitable stand so that the
front wheel is elevated.
3. Remove:
Front brake caliper
NO ...