2021 YAMAHA MT-125 lock

Periodic maintenance an d a djustment
6-20
6 6. To increase the clutch lever free
play, turn the clutch lever free play
adjusting nut in direction (a). To
decrease the clutch lever free
play, turn the adjusting nut in di-
rection (b).
7. Tighten the locknut at the crank- case.
8. Tighten the locknut at the clutch lever and then slide the rubber
cover to its original position.
EAUT1223
Checkin g the front b rake lever
free playMeasure the front brake lever free play
as shown.
Periodically check the brake lever free
play and, if necessary, have a Yamaha
dealer check the brake system.
WARNING
EWA10642
An incorrect b rake lever free play in-
d icates a hazar dous con dition in the
b rake system. Do not operate the vehicle until the b
rake system has
b een checked or repaired by a
Yamaha dealer.1. Brake lever free playFront brake lever free play:
2.0–5.0 mm (0.08–0.20 in)
1
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Periodic maintenance an d a djustment
6-21
6
EAUM1355
A djustin g the brake pe dal free
playMeasure the brake pedal free play as
shown.
Periodically check the brake pedal free
play and, if necessary, have a Yamaha
dealer adjust it.
WARNING
EWAM1031
An incorrect brake pe dal free play
in dicates a hazar dous con dition in
the brake system. Do not operate the motorcycle until the
brake sys-
tem has b een checked or repaired
b y a Yamaha dealer.
EAU36505
Brake li ght switchesThe brake light should come on just
before braking takes effect. The brake
light is activated by switches connect-
ed to the brake lever and brake pedal.
Since the brake light switches are
components of the anti-lock brake sys-
tem, they should only be serviced by a
Yamaha dealer.
1. Brake pedal free playBrake pe dal free play:
7.0–13.0 mm (0.28–0.51 in)
1
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Periodic maintenance an d a djustment
6-23
6
Rear
brake
WARNING
EWA16011
Improper maintenance can result in
loss of b raking a bility. O bserve
these precautions:  Insufficient brake flui d may al-
low air to enter the brake sys-
tem, re ducin g brakin g
performance.
 Clean the filler cap before re-
movin g. Use only DOT 4 brake
flui d from a seale d container. 
Use only the specified b rake flu-
i d ; otherwise, the ru bber seals
may deteriorate, causin g leak-
a g e.
 Refill with the same type of
brake flui d. A dding a brake fluid
other than DOT 4 may result in a
harmful chemical reaction.
 Be careful that water or d ust
d oes not enter the brake flui d
reservoir when refillin g. Water
will si gnificantly lower the boil-
in g point of the flui d an d may re-
sult in vapor lock, an d d ir
t may
clo g the ABS hy draulic unit
valves.
NOTICE
ECA17641
Brake flui d may d amage painte d
surfaces or plastic parts. Always
clean up spilled fluid imme diately.As the brake pads wear, it is normal for
the brake fluid level to gradually go
down. A low brake fluid level may indi-
cate worn brake pads and/or brake
system leakage; therefore, be sure to
check the brake pads for wear and the
brake system for leakage. If the brake fluid level goes down suddenly, have a
Yamaha dealer check the cause before
further riding.
1. Minimum level markSpecifie
d b rake flui d:
DOT 4
1
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Periodic maintenance an d a djustment
6-24
6
EAU22734
Chan gin g the brake flui dHave a Yamaha dealer change the
brake fluid every 2 years. In addition,
have the seals of the master cylinders
and brake calipers, as well as the brake
hoses replaced at the intervals listed
below or sooner if they are damaged or
leaking.
 Brake seals: every 2 years
 Brake hoses: every 4 years
EAU22762
Drive chain slackThe drive chain slack should be
checked before each ride and adjusted
if necessary.
EAU74253
To check the drive chain slack
1. Place the motorcycle on the side- stand.TIPWhen checking and adjusting the drive
chain slack, there should be no weight
on the motorcycle.2. Shift the transmission into theneutral position.
3. Measure the drive chain slack as shown. 4. If the drive chain slack is incorrect,
adjust it as follows. NOTICE: Im-
proper drive chain slack will
overloa d the en gine as well as
other vital parts of the motorcy-
cle an d can lea d to chain slip-
pa ge or breakag e. To prevent
this from occurrin g, keep the
d rive chain slack within the
specifie d limits.
[ECA10572]
EAU3431B
To adjust the drive chain slack
Consult a Yamaha dealer before ad-
justing the drive chain slack. 1. Loosen the axle nut and the lock- nut on each side of the swingarm.
1. Drive chain slackZAUM1604
1
Drive chain slack:30.0–40.0 mm (1.18–1.57 in)
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Periodic maintenance an d a djustment
6-25
6
2. To tighten the drive chain, turn the drive chain slack adjusting bolt on
each side of the swingarm in di-
rection (a). To loosen the drive
chain, turn the adjusting bolt on
each side of the swingarm in di-
rection (b), and then push the rear
wheel forward.
TIPUsing the alignment marks on each
side of the swingarm, make sure that
both drive chain pullers are in the same
position for proper wheel alignment.
3. Tighten the axle nut, then the lock-nuts to their specified torques.
4. Make sure that the drive chain pullers are in the same position,
the drive chain slack is correct,
and the drive chain moves
smoothly.
EAU23026
Cleanin g an d lu bricatin g the
d rive chainThe drive chain must be cleaned and
lubricated at the intervals specified in
the periodic maintenance and lubrica-
tion chart, otherwise it will quickly wear
out, especially when riding in dusty or
wet areas. Service the drive chain as
follows.NOTICE
ECA10584
The drive chain must b e lubricate d
after washin g the motorcycle, ri din g
in the rain or ri din g in wet areas.1. Clean the drive chain with kero-
sene and a small soft brush.
NOTICE: To prevent d amaging
the O-rin gs, do not clean the
d rive chain with steam cleaners,
hi gh-pressure washers or inap-
propriate solvents.
[ECA11122]
2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a special O-ring chain
lubricant. NOTICE: Do not use
en gine oil or any other lu bri-
cants for the drive chain, as they
1. Drive chain slack adjusting bolt
2. Axle nut
3. Alignment marks
4. LocknutZAUM1605
321
4
(b)
(a)
Ti
ghtenin g torques:
Axle nut: 85 N·m (8.5 kgf·m, 63 lb·ft)
Locknut:
15 N·m (1.5 kgf·m, 11 lb·ft)
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Periodic maintenance an d a djustment
6-33
6
EAU62590
Replacin g a turn sig nal light
b ul b1. Remove the turn signal light lens
by removing the screw.
2. Remove the turn signal light bulb socket (together with the bulb) by
turning it counterclockwise. 3. Remove the burnt-out bulb by
pulling it out.
4. Insert a new bulb into the socket.
5. Install the socket (together with the bulb) by turning it clockwise.
6. Install the turn signal light lens by installing the screw. NOTICE: Do
not overti ghten the screw, oth-
erwise the lens may break.
[ECA11192] EAUM3510
Replacin
g the license plate
lig ht bul b1. Remove the license plate light unit
by removing the screw.
2. Remove the license plate light bulb socket (together with the
bulb) by pulling it out.
3. Remove the burnt-out bulb by pulling it out.
4. Insert a new bulb into the socket.
5. Install the socket (together with the bulb) by pushing it in.
6. Install the license plate light unit by installing the screw.
1. Screw
1
1. Turn signal light bulbZAUM1609
1
1. License plate light bulb socket
2. License plate light unit
3. ScrewZAUM1621
2
3
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Periodic maintenance an d a djustment
6-36
6
EAU86420
En gine overheatin g
WARNING
EWAT1041
Do not remove the ra diator cap when the en gine an d ra diator are hot. Scal din g hot flui d an d steam may be
b lown out un der pressure, which coul d cause serious injury. Be sure to wait until the en gine has coole d.
 Place a thick ra g, like a towel, over the ra diator cap, an d then slowly rotate the cap counterclockwise to the
d etent to allow any resi dual pressure to escape. When the hissin g soun d has stoppe d, press d own on the cap
while turnin g it counterclockwise, an d then remove the cap.TIPIf coolant is not available, tap water can be temporarily used instead, provided that it is changed to the recommended cool-
ant as soon as possible.
Wait until the
engine has cooled.
Check the coolant level in the
reservoir and radiator.
The coolant level
is OK.The coolant level is low.
Check the cooling system
for leakage.
Have a Yamaha dealer checkand repair the cooling system.Add coolant. (See TIP.)
Start the engine. If the engine overheats again,
have a
Yamaha dealer check
and repair the cooling system.
There is
leakage.
There is
no leakage.
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10-1
10
IndexAABS ....................................................... 3-15
ABS warning light ................................... 3-3
Air filter element and check hose,
replacing and cleaning ....................... 6-14BBattery .................................................. 6-30
Brake and clutch levers, checking and lubricating ........................................... 6-27
Brake and shift pedals, checking and lubricating ........................................... 6-27
Brake fluid, changing ............................ 6-24
Brake fluid level, checking .................... 6-22
Brake lever ............................................ 3-14
Brake light switches.............................. 6-21
Brake pedal........................................... 3-14
Brake pedal free play, adjusting ........... 6-21CCables, checking and lubricating ......... 6-26
Canister................................................... 6-9
Care ........................................................ 7-1
Catalytic converter ................................ 3-19
Clutch lever ........................................... 3-13
Clutch lever free play, adjusting ........... 6-19
Coolant ................................................. 6-13
Coolant temperature warning light ......... 3-2
Cowlings, removing and installing .......... 6-8DData recording, vehicle ........................... 9-2
Diagnostic connector.............................. 9-2
Dimmer switch ...................................... 3-13
Drive chain, cleaning and lubricating .... 6-25
Drive chain slack................................... 6-24
EEngine break-in ...................................... 5-1
Engine idling speed .............................. 6-15
Engine oil and oil filter element ............ 6-10
Engine overheating ............................... 6-36
Engine serial number .............................. 9-1FFront and rear brake pads, checking ... 6-22
Front brake lever free play, checking ... 6-20
Front fork, checking ............................. 6-29
Fuel ....................................................... 3-16
Fuel consumption, tips for reducing ...... 5-4
Fuel tank breather hose and overflow hose ................................................... 3-18
Fuel tank cap ........................................ 3-16
Fuses, replacing ................................... 6-31HHandlebar switches .............................. 3-12
Helmet holder ....................................... 3-20
High beam indicator light ....................... 3-2
Horn switch .......................................... 3-13IIdentification numbers ............................ 9-1
Ignition circuit cut-off system ............... 3-21
Indicator lights and warning lights ......... 3-2LLicense plate light bulb, replacing........ 6-33MMain switch/steering lock....................... 3-1
Maintenance and lubrication, periodic ... 6-4
Maintenance, emission control system.................................................. 6-3
Malfunction indicator light (MIL) ............. 3-3
Matte color, caution ............................... 7-1 Model label .............................................9-1
Multi-function meter unit .........................3-4
NNeutral indicator light ..............................3-2PParking ....................................................5-4
Part locations ..........................................2-1
Pass switch ...........................................3-13RRear suspension, lubricating ................6-28SSafety information ...................................1-1
Seat .......................................................3-19
Shifting ....................................................5-3
Shift light .................................................3-3
Shift pedal .............................................3-14
Sidestand ..............................................3-20
Sidestand, checking and lubricating.....6-28
Spark plug, checking ..............................6-8
Specifications .........................................8-1
Start/Engine stop switch .......................3-13
Starting the engine ..................................5-2
Steering, checking ................................6-29
Storage ...................................................7-3
Supporting the motorcycle ...................6-34TTail/brake light ......................................6-32
Throttle grip and cable, checking and
lubricating ...........................................6-26
Throttle grip free play, adjusting ...........6-16
Tires ......................................................6-17
Tool kit ....................................................6-2
Troubleshooting ....................................6-34
Troubleshooting chart ...........................6-35
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