2020 YAMAHA MT-125 check engine

Periodic maintenance and adjustment
6-36
6
EAU86390
Troubleshooting chart
1. FuelThere is enough fuel.
There is no fuel.
Check the battery.
Supply fuel.
The engine turns over
quickly.
The engine turns over
slowly.
Try starting the
engine.
The engine does not
start.
Check the battery.
Wipe off with a dry
cloth and correct the
spark plug gap, or
replace the spark
plug(s).
Check the battery
lead connections,
and charge the
battery if necessary.
2. BatteryThe battery is good.
The engine does not
start.
Check the ignition.
3. IgnitionWet
Dry
There is compression.
There is no
compression.
The engine does not start.
Have a Yamaha dealer check the vehicle.
Have a Yamaha dealer check the vehicle.
The engine does not
start.
Check the
compression.Have a Yamaha
dealer check the
vehicle.
Remove the spark
plug and check
the electrodes.
Operate the electric
starter.
Try starting the
engine.
Check the fuel level
in the fuel tank.
4. Compression
UB6GE0E0.book Page 36 Wednesday, August 28, 2019 11:11 AM

Periodic maintenance and adjustment
6-37
6
EAU86430Engine overheating
WARNING
EWAT1041
Do not remove the radiator cap when the engine and radiator are hot.
Scalding hot fluid and steam may be blown out under pressure, which
could cause serious injury. Be sure to wait until the engine has cooled.
Place a thick rag, like a towel, over the radiator cap, and then slowly ro-
tate the cap counterclockwise to the detent to allow any residual pres-
sure to escape. When the hissing sound has stopped, press down on the
cap while turning it counterclockwise, and then remove the cap.
TIP
If coolant is not available, tap water can be temporarily used instead, provided
that it is changed to the recommended coolant as soon as possible.
Wait until the engine
has cooled.
Check the coolant
level in the reservoir
and radiator.Add coolant.
(See TIP.)
The coolant level is
OK.
There is no leakage.
There is leakage.
The coolant level is
low.
Check the cooling
system for leakage.
Have a Yamaha
dealer check and
repair the cooling
system.
Start the engine. If the engine overheats again,
have a Yamaha dealer check and repair the cooling
system.
UB6GE0E0.book Page 37 Wednesday, August 28, 2019 11:11 AM

Consumer information
9-3
9
EAU85300
Vehicle data recording
This model’s ECU stores certain vehi-
cle data to assist in the diagnosis of
malfunctions and for research, statisti-
cal analysis and development purpos-
es.
Although the sensors and recorded
data will vary by model, the main data
points are:
Vehicle status and engine perfor-
mance data
Fuel-injection and emission-relat-
ed data
This data will be uploaded only when a
special Yamaha diagnostic tool is at-
tached to the vehicle, such as when
maintenance checks or service proce-
dures are performed.
Vehicle data uploaded will be handled
appropriately according to the follow-
ing Privacy Policy.
Privacy Policy
Yamaha will not disclose this data to a
third party except in the following cas-
es. In addition, Yamaha may provide
vehicle data to a contractor in order to
outsource services related to the han-
dling of vehicle data. Even in this case,
Yamaha will require the contractor to
properly handle the vehicle data we
provided and Yamaha will appropriate-
ly manage the data.
With the consent of the vehicle
owner
Where obligated by law
For use by Yamaha in litigation
When the data is not related to an
individual vehicle nor owner
https://www.yamaha-motor.eu/eu/
privacy/privacy-policy.aspx
UB6GE0E0.book Page 3 Wednesday, August 28, 2019 11:11 AM

10-1
10
Index
A
ABS ....................................................... 3-15
ABS warning light ................................... 3-3
Air filter element and check hose,
replacing and cleaning ....................... 6-13
B
Battery .................................................. 6-30
Brake and clutch levers, checking and
lubricating ........................................... 6-27
Brake and shift pedals, checking and
lubricating ........................................... 6-26
Brake fluid, changing ............................ 6-23
Brake fluid level, checking .................... 6-22
Brake lever ............................................ 3-14
Brake light switches.............................. 6-20
Brake pedal........................................... 3-14
Brake pedal free play, adjusting ........... 6-20
C
Cables, checking and lubricating ......... 6-25
Care ........................................................ 7-1
Catalytic converter ................................ 3-18
Clutch lever ........................................... 3-13
Clutch lever free play, adjusting ........... 6-18
Coolant ................................................. 6-11
Coolant temperature warning light ......... 3-2
Cowlings, removing and installing .......... 6-7
D
Data recording, vehicle ........................... 9-3
Diagnostic connectors ............................ 9-2
Dimmer switch ...................................... 3-12
Drive chain, cleaning and lubricating .... 6-25
Drive chain slack................................... 6-23
E
Engine break-in....................................... 5-1
Engine idling speed .............................. 6-13
Engine oil and oil filter element ............... 6-8
Engine overheating ............................... 6-37
Engine serial number .............................. 9-1
Engine trouble warning light ................... 3-3
F
Front and rear brake pads, checking.... 6-21
Front brake lever free play, checking ... 6-19
Front fork, checking .............................. 6-28
Fuel ....................................................... 3-16
Fuel consumption, tips for reducing ....... 5-5
Fuel tank cap ........................................ 3-16
Fuel tank overflow hose ........................ 3-18
Fuses, replacing.................................... 6-31
H
Handlebar switches .............................. 3-12Helmet holder ....................................... 3-20
High beam indicator light ....................... 3-2
Horn switch .......................................... 3-12
I
Identification numbers ............................ 9-1
Ignition circuit cut-off system............... 3-21
Indicator lights and warning lights ......... 3-2
L
License plate light bulb, replacing........ 6-34
M
Main switch/steering lock....................... 3-1
Maintenance and lubrication, periodic ... 6-4
Maintenance, emission control
system.................................................. 6-3
Matte color, caution ............................... 7-1
Model label ............................................. 9-1
Multi-function meter unit ........................ 3-4
N
Neutral indicator light ............................. 3-2
P
Parking ................................................... 5-6
Part locations ......................................... 2-1
Pass switch .......................................... 3-12
S
Safety information .................................. 1-1
Seat ...................................................... 3-19
Shifting ................................................... 5-4
Shift light ................................................ 3-3
Shift pedal ............................................ 3-13
Sidestand ............................................. 3-20
Sidestand, checking and lubricating .... 6-27
Spark plug, checking ............................. 6-7
Specifications ......................................... 8-1
Start/Engine stop switch ...................... 3-12
Starting the engine ................................. 5-2
Steering, checking................................ 6-29
Storage ................................................... 7-4
Supporting the motorcycle................... 6-34
Swingarm pivots, lubricating ................ 6-28
T
Tail/brake light ...................................... 6-33
Throttle grip and cable, checking and
lubricating .......................................... 6-26
Throttle grip free play, adjusting........... 6-14
Tires ...................................................... 6-15
Tool kit.................................................... 6-2
Troubleshooting ................................... 6-35
Troubleshooting chart .......................... 6-36
Turn signal indicator light ....................... 3-2
Turn signal light bulb, replacing ........... 6-33
UB6GE0E0.book Page 1 Wednesday, August 28, 2019 11:11 AM