2018 YAMAHA MT-125 radiator

Instrument and control functions
3-7
3
NOTICE
ECA10022
Do not continue to operate the en-
gine if it is overheating.
TIP
Coolant temperature varies with
changes in the weather and en-
gine load.
The radiator fan will automatically
switch on or off according to the
coolant temperature.
If the engine overheats, see page
6-39 for further instruction.
Odometer and tripmeter display
The odometer and tripmeter display is
equipped with:
an odometer
two tripmeters
a fuel reserve tripmeter
Push the “SELECT” button to switch
between the odometer and the tripme-
ters in the following order:
ODO (odometer) → TRIP 1 (tripmeter)
→ TRIP 2 (tripmeter) → ODO (odome-
ter)When approximately 3.0 L (0.79 US
gal, 0.66 Imp.gal) of fuel remains in the
fuel tank, the display will automatically
change to the fuel reserve tripmeter
mode “F TRIP” and start counting the
distance traveled from that point. In
this case, push the “SELECT” button
to switch the display in the following
order:
F TRIP → ODO → TRIP 1 → TRIP 2 →
F TRIP
To manually reset a tripmeter, select it
with the “SELECT” button, and then
push the “RESET” button for two sec-
onds.
TIP
The fuel reserve tripmeter will re-
set automatically and disappear
after you have refueled and turned
the key to “OFF”.
The tripmeters will automatically
reset and continue counting after
999.9 is reached.
The odometer will lock at 199999
and cannot be reset.
1. Odometer/tripmeter/fuel reserve tripmeter
1/2
ZAUM1305
TRIP1
1
1. Odometer/tripmeter/fuel reserve tripmeter
1/2
ZAUM1306
F TRIP
1
UBR3E1E0.book Page 7 Wednesday, August 10, 2016 9:45 AM

Periodic maintenance and adjustment
6-13
6 3. If the coolant is at or below the
minimum level mark, remove
cowling A (See page 6-7.), and
then open the reservoir cap.
WARNING! Remove only the
coolant reservoir cap. Never at-
tempt to remove the radiator
cap when the engine is hot.
[EWA15162]
4. Add coolant to the maximum level
mark, and then close the reservoir
cap. NOTICE: If coolant is not
available, use distilled water or
soft tap water instead. Do not
use hard water or salt water
since it is harmful to the engine.
If water has been used instead
of coolant, replace it with cool-
ant as soon as possible, other-
wise the cooling system will not
be protected against frost and
corrosion. If water has been
added to the coolant, have a
Yamaha dealer check the anti-
freeze content of the coolant as
soon as possible, otherwise the
effectiveness of the coolant will
be reduced.
[ECA10473]
5. Install the cowling.
EAU33032Changing the coolant
The coolant must be changed at the in-
tervals specified in the periodic mainte-
nance and lubrication chart. Have a
Yamaha dealer change the coolant.WARNING! Never attempt to remove
the radiator cap when the engine is
hot.
[EWA10382]
Coolant reservoir capacity (up to
the maximum level mark):
0.25 L (0.26 US qt, 0.22 Imp.qt)
UBR3E1E0.book Page 13 Wednesday, August 10, 2016 9:45 AM

Periodic maintenance and adjustment
6-33
6
3. Turn the key to “ON” and turn on
the electrical circuit in question to
check if the device operates.
4. If the fuse immediately blows
again, have a Yamaha dealer
check the electrical system.
EAUM3501
Replacing the headlight bulb
This model is equipped with a halogen
bulb headlight. If the headlight bulb
burns out, replace it as follows.
NOTICE
ECA10651
Take care not to damage the follow-
ing parts:
Headlight bulb
Do not touch the glass part of
the headlight bulb to keep it free
from oil, otherwise the transpar-
ency of the glass, the luminosity
of the bulb, and the bulb life will
be adversely affected. Thor-
oughly clean off any dirt and fin-
gerprints on the headlight bulb
using a cloth moistened with al-
cohol or thinner.
Headlight lens
Do not affix any type of tinted
film or stickers to the headlight
lens.
Do not use a headlight bulb of a
wattage higher than specified.
1. Remove the headlight unit by re-
moving the bolts on each side.
1. Headlight fuse
2. Signaling system fuse
3. Ignition fuse
4. Radiator fan motor fuse
5. Main fuse
6. ABS control unit fuse
7. Spare fuse
8. Backup fuse
9. ABS solenoid fuse
10.ABS motor fuse
Specified fuses:
Main fuse:
20.0 A
Ignition fuse:
7.5 A
Signaling system fuse:
7.5 A
Headlight fuse:
15.0 A
Radiator fan motor fuse:
5.0 A
ABS control unit fuse:
10.0 A
ABS motor fuse:
30.0 A
ABS solenoid fuse:
20.0 A
Backup fuse:
10.0 A
ZAUM1231
10
303020
7
8
91010
157.5
207.5 7.515
5 20
5
7
12
3
45
6
1. Do not touch the glass part of the bulb.
UBR3E1E0.book Page 33 Wednesday, August 10, 2016 9:45 AM

Periodic maintenance and adjustment
6-39
6 Engine overheating
WARNING
EWA10401
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.
After removing the radiator cap retaining bolt, place a thick rag, like a
towel, over the radiator cap, and then slowly rotate the cap counter-
clockwise to the detent to allow any residual pressure 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.
UBR3E1E0.book Page 39 Wednesday, August 10, 2016 9:45 AM

Specifications
8-1
8
Dimensions:
Overall length:
1950 mm (76.8 in)
Overall width:
745 mm (29.3 in)
Overall height:
1025 mm (40.4 in)
Seat height:
810 mm (31.9 in)
Wheelbase:
1350 mm (53.1 in)
Ground clearance:
140 mm (5.51 in)
Minimum turning radius:
2.5 m (8.20 ft)
Weight:
Curb weight:
141 kg (311 lb)
Engine:
Engine type:
Liquid cooled 4-stroke, SOHC
Cylinder arrangement:
Single cylinder
Displacement:
124 cm³
Bore × stroke:
52.0 × 58.6 mm (2.05 × 2.31 in)
Compression ratio:
11.2 : 1
Starting system:
Electric starter
Lubrication system:
Wet sump
Engine oil:
Recommended brand:
YAMALUBE
Type:
SAE 10W-40
Recommended engine oil grade:
API service SG type or higher, JASO
standard MA
Engine oil quantity:
Without oil filter element replacement:
0.95 L (1.00 US qt, 0.84 Imp.qt)
With oil filter element replacement:
1.00 L (1.06 US qt, 0.88 Imp.qt)
Coolant quantity:
Coolant reservoir (up to the maximum level
mark):
0.25 L (0.26 US qt, 0.22 Imp.qt)Radiator (including all routes):
1.00 L (1.06 US qt, 0.88 Imp.qt)
Air filter:
Air filter element:
Dry element
Fuel:
Recommended fuel:
Premium unleaded gasoline (Gasohol [E10]
acceptable)
Fuel tank capacity:
11.5 L (3.04 US gal, 2.53 Imp.gal)
Fuel reserve amount:
3.0 L (0.79 US gal, 0.66 Imp.gal)
Fuel injection:
Throttle body:
ID mark:
BR61 00
Spark plug(s):
Manufacturer/model:
NGK/CR9E
Spark plug gap:
0.7–0.8 mm (0.028–0.031 in)
Clutch:
Clutch type:
Wet, multiple-disc
Drivetrain:
Primary reduction ratio:
73/24 (3.042)
Final drive:
Chain
Secondary reduction ratio:
48/14 (3.429)
Transmission type:
Constant mesh 6-speed
Operation:
Left foot operation
Gear ratio:
1st:
34/12 (2.833)
2nd:
30/16 (1.875)
3rd:
30/22 (1.364)
4th:
24/21 (1.143)
5th:
22/23 (0.957)
6th:
21/25 (0.840)
UBR3E1E0.book Page 1 Wednesday, August 10, 2016 9:45 AM

Specifications
8-3
8
Brake/tail light:
LED
Front turn signal light:
10.0 W × 2
Rear turn signal light:
10.0 W × 2
Auxiliary light:
LED
License plate light:
5.0 W × 1
Meter lighting:
LED
Neutral indicator light:
LED
High beam indicator light:
LED
Turn signal indicator light:
LED
Fuel level warning light:
LED
Engine trouble warning light:
LED
ABS warning light:
LED
Fuse(s):
Main fuse:
20.0 A
Headlight fuse:
15.0 A
Signaling system fuse:
7.5 A
Ignition fuse:
7.5 A
Radiator fan motor fuse:
5.0 A
ABS control unit fuse:
10.0 A
ABS motor fuse:
30.0 A
ABS solenoid fuse:
20.0 A
Backup fuse:
10.0 A
UBR3E1E0.book Page 3 Wednesday, August 10, 2016 9:45 AM