Yamaha YZF-R125 Service Manual: Checking the bulbs and bulb sockets
NOTE:
Do not check any of the lights that use LEDs.
Check each bulb and bulb socket for damage or wear, proper connections, and also for continuity between the terminals.
Damage/wear
Repair or replace
the bulb,
bulb socket or both.
Improperly connected 
Properly
connect.
No continuity 
Repair or replace the
bulb, bulb
socket or both.
Checking the switches
1. Clutch switch
2. Main switch
3. Front brake light switch
4. Sidestand switch
5. Rear brake light switch
6. Neutral switch
7. Turn signal switch
8. Horn switch
9. Dimmer switch
10.Pass ...
Types of bulbs
The bulbs used on this vehicle are shown in the
illustration.
Bulbs "a" and "b" are used for the headlights
and usually use a bulb holder that must be detached
before removing the bulb. The m ...
Other materials:
Checking the shift drum assembly
1. Check:
Shift drum groove
Damage/scratches/wear Replace
the shift
drum assembly.
Shift drum segment "1"
Damage/wear Replace the
shift drum assembly.
Shift drum bearing "2"
Damage/pitting Replace the
shift drum assembly.
...
Installing the steering head
1. Lubricate:
Upper bearing
Lower bearing
Bearing races
2. Install:
Lower ring nut
Rubber washer
Upper ring nut
Lock washer
Refer to "CHECKING AND ADJUSTING
THE STEERING HEAD" on page 3-22.
3. Install:
Upper bracket
Steering stem nut
NOTE:
Temporarily tighten t ...
Checking the valves and valve guides
The following procedure applies to all of the
valves and valve guides.
1. Measure:
Valve-stem-to-valve-guide clearance
Out of specification Replace the
valve
guide.
Valve-stem-to-valve-guide clearance =
Valve guide inside diameter "a" -
Valve stem diameter "b"
2. Replace:
...