Page 40 of 74

NOTE:
The coolant should be between the
minimum and maximum level marks.
4. If the coolant is at or below the
minimum level mark, open the
reservoir cap, add coolant to the
maximum level mark, and then
close the reservoir cap.
Coolant reservoir capacity:
0,3 L (0,32 US qt)
ECA10470
CAUTION
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 coo-
lant as soon as possible, other-
wise the engine may not be
sufficiently cooled and the coo-
ling system will not be protec-
ted against frost and corrosion.
If water has been added to the
coolant, have a Yamaha dealer
check the antifreeze content of
the coolant as soon as possi-
ble, otherwise the effective-
ness of the coolant will be
reduced.
EWA10380
s s
WARNING
Never attempt to remove the radia-
tor cap when the engine is hot.
5. Install the panel.
NOTE:
If the engine overheats, see page
6-31 for further instructions.
EAU20370
To change the coolant
1. Radiator cap bolt
2. Radiador cap
1. Put the vehicle on a level place.
2. Remove cowling C and panel D.
(See page 6-5 ~ 6-6.)
3. Remove the radiator cap stopper
bolt and the radiator cap.
1. Drain bolt
4. Place a container under the engi-
ne and remove the coolant drain
bolt.
5. Disconnect the coolant reservoir
hose on the reservoir side and
drain the coolant from the reser-
voir.
6. After draining the coolant, tho-
roughly flush the cooling system
with clean tap water.
7. Replace the coolant drain bolt
washer if it is damaged, and then
tighten the coolant drain bolt to
the specified torque.6
PERIODIC MAINTENANCE AND MINOR REPAIR
6-9
2
11
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Page 41 of 74

Tightening torque:
Coolant drain bolt:
10 Nm (1,0 m•kgf)
8. Connect the coolant reservoir
hose.
9. Pour the recommended coolant
into the radiator until it is full.
Recommended antifreeze:
High quality ethylene glycol antifree-
ze containing corrosion inhibitors for
aluminum engines
Antifreeze/water mixing ratio:
1:1
Coolant quantity:
Radiator capacity (including all rou-
tes):
0,92 L (0,97 US qt)
Coolant reservoir capacity:
0,3 L (0,32 US qt)
ECA10470
CAUTION
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 coo-
lant as soon as possible, other-
wise the engine may not be
sufficiently cooled and the coo-
ling system will not be protec-
ted against frost and corrosion.
If water has been added to the
coolant, have a Yamaha dealer
check the antifreeze content of
the coolant as soon as possi-
ble, otherwise the effective-
ness of the coolant will be
reduced.
10. Install the radiator cap.
11. Run the engine several minutes.
Stop the engine and recheck the
coolant level in the radiator. If it is
low, add more coolant until it rea-
ches the top of the radiator.
12. Install the radiator cap stopper
bolt.
13. Fill the coolant reservoir with
coolant up to maximum level.
14. Install the coolant reservoir cap
and check for coolant leakage.
NOTE:
If any leakage is found, ask a Yamaha
dealer to inspect the cooling system.
15. Install the cowling and the panel.
EAU20831
Cleaning the air filter
element and check hose
The air filter element should be clea-
ned at the intervals specified in the
periodic maintenance and lubrication
chart. Clean the air filter element more
frequently if you are riding in unu-
sually wet or dusty areas. In addition,
the air filter check hose must be fre-
quently checked and cleaned if
necessary.
1. Screws (x3)
6
PERIODIC MAINTENANCE AND MINOR REPAIR
6-10
1
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Page 67 of 74

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
8-1
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