Yamaha YZF-R125 Service Manual: Checking the condition of the bulb sockets
The following procedure applies to all of the bulb sockets.
1. Check:
Bulb socket (for continuity)
(with the pocket tester)
No continuity 
Replace.
NOTE:
Check each bulb socket for continuity in the same manner as described in the bulb section, however, note the following.
a. Install a good bulb into the bulb socket.
b. Connect the pocket tester probes to the respective leads of the bulb socket.
c. Check the bulb socket for continuity. If any of the readings indicate no continuity, replace the bulb socket.
Checking the condition of the bulbs
The following procedure applies to all of the
bulbs.
1. Remove:
Bulb
WARNINGSince the headlight bulbs get extremely
hot,
keep flammable products and your hands
away from them ...
Checking the fuses
The following procedure applies to all of the fuses.
CAUTION:To avoid a short circuit, always turn the
main
switch to "OFF" when checking or replacing
a fuse.
1. Remove:
Ri ...
Other materials:
Checking the shift forks
The following procedure applies to all of the shift
forks.
1. Check:
Shift fork cam follower "1"
Shift fork pawl "2"
Bends/damage/scoring/wear
Replace the
shift fork.
2. Check:
Shift fork guide bar
Roll the shift fork guide bar on a flat surface.
Bends Replace. ...
Replacing a turn signal light bulb
Remove the turn signal light lens
by removing the screw.
Screw
Remove the burnt-out bulb by
pushing it in and turning it counterclockwise.
Insert a new bulb into the socket,
push it in, and then turn it clockwise
until it stops.
Install the lens by installing ...
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
is too loose can skip and damage the swingarm
or cause an accident. Therefore, keep
the drive ...