Tightening torque:
Spark plug:
20 Nm (2 m•kgf)
NOTE:
If a torque wrench is not available
when installing a spark plug, a good
estimate of the correct torque is
1/4–1/2 turn past finger tight. Howe-
ver, the spark plug should be tighte-
ned to the specified torque as soon
as possible.
EAU19950
Transmission oil
1. Oil level window
2. Maximum level mark
3. Minimum level mark
The transmission oil level should be
checked before each ride. In addition,
the transmission oil must be changed
at the intervals specified in the perio-
dic maintenance and lubrication
chart.
To check the transmission oil level
1. Place the vehicle on a level surfa-
ce and hold it in an upright posi-
tion.
NOTE:
Make sure that the vehicle is positio-
ned straight up when checking the oil
level. A slight tilt to the side can result
in a false reading.
1. Plug to fill with oil
2. Start the engine, warm it up for
several minutes, and then turn it
off.
3. Wait a few minutes until the oil
settles, and then check the oil
level through the check window
located at the right side of the
crankcase.
NOTE:
The transmission oil should be at or
above the minimum level mark.
4. If the oil is below the minimum
level mark, remove the oil filler
cap, add sufficient oil of the
recommended type to raise it to
the correct level, and then install
and tighten the cap.
To change the transmission oil
1. Drain bolt
6
PERIODIC MAINTENANCE AND MINOR REPAIR
6-7
2
3
11
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To clean the air filter element
1. Remove panel E. (See page 6-6.)
2. Remove the air filter case cover
by removing the screws.
3. Pull the air filter element out.
1. Guide
2. Filter
4. Remove the sponge material
from the air filter element frame,
clean it with solvent, and then
squeeze the remaining solvent
out.5. Apply oil of the recommended
type to the entire surface of the
sponge material, and then sque-
eze the excess oil out.
NOTE:
The sponge material should be wet
but not dripping.
Recommended oil:
Foam air filter oil
6. Pull the sponge material over the
air filter element frame.
7. Insert the element into the air fil-
ter case.
ECA10480
CAUTION
Make sure that the air filter ele-
ment is properly seated in the
air filter case.
The engine should never be
operated without the air filter
element installed, otherwise
the piston(s) and/or cylinder(s)
may become excessively worn.
8. Install the air filter case cover by
installing the screws.
9. Install the panel.To clean the air filter check hose
1. Check the hose at the bottom of
the air filter case for accumulated
dirt or water.
2. If dirt or water is visible, remove
the hose, clean it, and then install
it.
EAU21280
Adjusting the carburetor
The carburetor is an important part of
the engine and requires very sophisti-
cated adjustment. Therefore, most
carburetor adjustments should be left
to a Yamaha dealer, who has the
necessary professional knowledge
and experience. The adjustment des-
cribed in the following section, howe-
ver, may be serviced by the owner as
part of routine maintenance.
ECA10550
CAUTION
The carburetor has been set and
extensively tested at the Yamaha
factory. Changing these settings
without sufficient technical know-
ledge may result in poor perfor-
mance of or damage to the engine.
6
PERIODIC MAINTENANCE AND MINOR REPAIR
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Recommended brake fluid:
DOT 4
Refill with the same type of brake
fluid. Mixing fluids may result in a
harmful chemical reaction and
lead to poor braking performan-
ce.
Be careful that water does not
enter the brake fluid reservoir
when refilling. Water will signifi-
cantly lower the boiling point of
the fluid and may result in vapor
lock.
Brake fluid may deteriorate pain-
ted surfaces or plastic parts.
Always clean up spilled fluid
immediately.
As the brake pads wear, it is nor-
mal for the brake fluid level to
gradually go down. However, if
the brake fluid level goes down
suddenly, have a Yamaha dealer
check the cause.
EAU22730
Changing the brake fluid
Have a Yamaha dealer change the
brake fluid at the intervals specified in
the NOTE after the periodic mainte-
nance and lubrication chart. In addi-
tion, have the oil seals of the master
cylinders and calipers as well as the
brake hoses replaced at the intervals
listed below or whenever they are
damaged or leaking.
Oil seals: Replace every two
years.
Brake hoses: Replace every four
years.
EAU22770
To check the drive chain slack
(a) Chain tension
1. Place the motorcycle on a level
surface and hold it in an upright
position.
NOTE:
When checking and adjusting the dri-
ve chain slack, the motorcycle should
be positioned straight up and there
should be no weight on it.
2. Shift the transmission into the
neutral position.
3. Move the rear wheel by pushing
the motorcycle to locate the tigh-
test portion of the drive chain,
and then measure the drive chain
slack as shown.
Drive chain slack:
45-55 mm (1,76-2,15 in)
4. If the drive chain slack is inco-
rrect, adjust it as follows.
6
PERIODIC MAINTENANCE AND MINOR REPAIR
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This model is equipped with quartz
bulb headlights. If a headlight bulb
burns out, replace it as follows.
1. Remove cowling A. (See page
6-5.)
2. Disconnect the headlight coupler,
and then remove the headlight
bulb cover.
3. Remove the headlight bulb hol-
der according to the following
illustration, and then remove the
defective bulb.
NOTE:
The removal procedure depends on
the type of bulb holder installed on
your vehicle.
EWA10790
s s
WARNING
Headlight bulbs get very hot. The-
refore, keep flammable products
away from a lit headlight bulb, and
do not touch the bulb until it has
cooled down.
4. Place a new bulb into position,
and then secure it with the bulb
holder.
ECA10660
CAUTION
Do not touch the glass part of the
headlight bulb to keep it free from
oil, otherwise the transparency of
the glass, the luminosity of the
bulb, and the bulb life will be adver-
sely affected. Thoroughly clean off
any dirt and fingerprints on the
headlight bulb using a cloth mois-
tened with alcohol or thinner.
5. Install the bulb cover, and then
connect the coupler.
6. Install the cowling.
7. Have a Yamaha dealer adjust the
headlight beam if necessary.
EAU24131
Replacing the tail/brake light
bulb
1. Screw (x2)
2. Lens
1. Remove the tail/brake light lens
by removing the screws.
2. Remove the defective bulb by
pushing it in and turning it coun-
terclockwise.
3. Insert a new bulb into the socket,
push it in, and then turn it clock-
wise until it stops.
4. Install the lens by installing the
screws.6
PERIODIC MAINTENANCE AND MINOR REPAIR
6-25
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DimensionsOverall length
DT125RE 2210 mm
DT125X 2139 mm
Overall width
795 mm
Overall height
DT125RE 1200 mm
DT125X 1121 mm
Seat height
DT125RE 900 mm
DT125X 886 mm
Wheelbase
DT125RE 1415 mm
DT125X 1396 mm
Ground clearance
DT125RE 300 mm
DT125X 271 mm
Minimum turning radius
DT125RE 2100 mm
DT125X 2016 mm
WeightWith oil and fuel
DT125RE 126.0 kg
DT125X 134.0 kg
EngineEngine type
Liquid cooled 2-stroke
Cylinder arrangement
Forward-inclined single cylinder
Displacement
124.0 cm
3
Bore x stroke
56.0 x 50.7 mmCompression ratio
6.70 :1
Starting system
Electric starter
Lubrication system
Separate lubrication (Yamaha autolube)
Type
YAMALUBE 2-cycle oil or 2-stroke engine
oil (JASO FC g
Engine oil quantityQuantity
1.3 L
Transmission oilType
SAE10W30 type SE motor oil
Oil change quantity
0.75 L
Cooling systemCoolant reservoir capacity (up to the maxi-
mum leve
0.30 L
Radiator capacity (including all routes)
0.92 L
Air filterAir filter element
Wet element
FuelRecommended fuel
Regular unleaded gasoline only
Fuel tank capacity
10.7 L
Fuel reserve amount
1.8 L
CarburetorManufacturer
MIKUNI
Type x quantity
TM28-92 x1
Spark plug(s)Manufacturer/model
NGK/BR8ES
Spark plug gap
0.7-0.8 mm
Clutch type
Wet, multiple-disc
TransmissionPrimary reduction system
Helical gear
Primary reduction ratio
71/22 (3.227)
Secondary reduction system
Chain drive
Secondary reduction ratio
57/16 (3.563)
Transmission type
Constant mesh 6-speed
Operation
Left foot operation
Gear ratio1st
34/12 (2.833)
2nd
30/16 (1.875)
3rd
24/17 (1.412)
4th
24/21 (1.143)
8
SPECIFICATIONS
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5th
22/23 (0.957)
6th
18/22 (0.818)
ChassisFrame type
Semi double cradle
Caster angle
DT125RE 27.00 degree
DT125X 24.50 degree
Trail
DT125RE 107.0 mm
DT125X 73.1 mm
Front tireType
With tube
Size
DT125RE 80/90-21 48P
DT125X 120/70-17 58H
Manufacturer/model
DT125RE MICHELIN/T63
DT125X PIRELLI/Sport Demon
Rear tireType
With tube
Size
DT125RE 110/80-18 58P
DT125X 140/70-17 66H
Manufacturer/model
DT125RE MICHELIN/T63
DT125X PIRELLI/Sport Demon
Maximum load
DT125RE 178 kg
DT125X 180 kg
Tire air pressure (measured on cold
tires)
Loading condition
0-90 kg
Front
DT125RE 150 kPa
DT125X 180 kPa
Rear
DT125RE 175 kPa
DT125X 200 kPa
Loading condition
90-178 kg
Front
DT125RE 175 kPa
DT125X 180 kPa
Rear
200 kPa
Off-road ridingFront
DT125RE 150 kPa
Rear
DT125RE 175 kPa
Front wheelWheel type
Spoke wheel
Rim size
DT125RE 21x1.60
DT125X 17x3.00
Rear wheelWheel type
Spoke wheel
Rim size
DT125RE 18x1.85
DT125X 17x3.50
Front brakeType
Single disc brake
Operation
Right hand operation
Recommended fluid
DOT 4
Rear brakeType
Single disc brake
Operation
Right foot operation
Recommended fluid
DOT 4
Front suspensionType
Telescopic fork
Spring/shock absorber type
Coil spring/oil damper
Wheel travel
DT125RE 270.0 mm
DT125X 200.0 mm
Rear suspensionType
Swingarm (link suspension)
Spring/shock absorber type
Coil spring/gas-oil damper
Wheel travel
DT125RE 260.0 mm
DT125X 230.0 mm
Electrical systemIgnition system
CDI
8
SPECIFICATIONS
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Charging system
AC magneto
BatteryModel
GT6B-3
Voltage, capacity
12 V, 6.0 Ah
HeadlightBulb type
Halogen bulb
Bulb voltage, wattage x quantityHeadlight
12 V, 600 W/55.0 W x 1
Tail/brake light
12 V, 21.0 W/5.0 W x 1
Front turn signal light
12 V, 10.0 W x 2
Rear turn signal light
12 V, 10.0 W x 2
Auxiliary light
12 V, 5.0 W x 1
Meter lighting
LED
Neutral indicator light
12 V, 3.0 W x 1
High beam indicator light
12 V, 3.0 W x 1
Oil level warning light
12 V, 3.0 W x 1
Turn signal indicator light
12 V, 3.0 W x 1
FusesMain fuse
15.0 A
8
SPECIFICATIONS
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