2015 YAMAHA WR 250F coolant temperature

FEATURES
1-6
EAS20170
FEATURES
EAS2GB2014OUTLINE OF THE FI SYSTEM
The main function of a fuel supply system is to provide fuel to the combustion chamber at the opti-
mum air-fuel ratio in accordance with the engine operating conditions and the atmospheric tempera-
ture. In the conventional carburetor system, the air-fuel ratio of the mixture to be supplied to the
combustion chamber is determined by the amount of intake air and fuel that is measured on the basis
of the jets to be used in the carburetor.
Despite the same amount of intake air, the fuel amount requirement varies with the engine operating
conditions (acceleration, deceleration, and operation under a heavy load). The carburetor that mea-
sures fuel through the use of jets are provided with various auxiliary devices, so that the optimum air
fuel ratio can be obtained to accommodate frequent changes in the operating conditions of the en-
gine. This model has adopted an electronically controlled fuel injection (FI) system, in place of the
conventional carburetor system. This system can obtain the optimum air-fuel ratio required by the
engine at all times by using a microprocessor that regulates the fuel injection amount according to
the engine operating conditions detected by various sensors.
1. Fuel injector
2. Throttle position sensor
3. Intake air pressure sensor
4. Engine trouble warning light
5. Intake air temperature sensor
6. ECU
7. Fuel pump
8. Battery
9. Lean angle sensor
10.Crankshaft position sensor
11.Coolant temperature sensor
12.Ignition coil
13.Speed sensor
748
9 10 116 5 123
12
13

FEATURES
1-7
EAS2GB2015FI SYSTEM
The fuel pump delivers fuel to the fuel injector via the fuel filter. The pressure regulator maintains the
fuel pressure that is applied to the fuel injector at only 324 kPa (3.24 kgf/cm
2, 47.0 psi). Accordingly,
when the energizing signal from the ECU energizes the fuel injector, the fuel passage opens, causing
the fuel to be injected into the intake manifold only during the time the passage remains open. There-
fore, the longer the length of time the fuel injector is energized (injection duration), the greater the
volume of fuel that is supplied. Conversely, the shorter the length of time the fuel injector is energized
(injection duration), the lesser the volume of fuel that is supplied.
The injection duration and the injection timing are controlled by the ECU. Signals input from the throt-
tle position sensor, the coolant temperature sensor, the crankshaft position sensor, the intake air
pressure sensor, and the intake air temperature sensor enable the ECU to determine the injection
duration. The injection timing is determined through the signals from the crankshaft position sensor.
As a result, the volume of fuel that is required by the engine can be supplied at all times in accordance
with the driving conditions.
1. Fuel pump
2. Fuel injector
3. ECU
4. Throttle position sensor
5. Coolant temperature sensor
6. Crankshaft position sensor
7. Intake air pressure sensor
8. Throttle body
9. Intake air temperature sensor
10.Air filter case
A. Fuel system
B. Intake system
C. Control system
1
23
5
6 7
8 9 10A
BC
4

ENGINE SPECIFICATIONS
2-7
Fuel pump
Pump type Electrical
Fuel injector
Model/quantity 30NA-FZ31/1
Resistance 12 
Throttle body
Type/quantity 30RA-A95R/1
ID mark 2GB1 00
Fuel line pressure at idling 324.0 kPa (3.24 kgf/cm
2, 47.0 psi)
Throttle position sensor
Resistance 6.30 k
Output voltage (at idle) 0.5 V
Fuel injection sensor
Crankshaft position sensor resistance 228–342  (Gy–B)
Intake air pressure sensor output voltage 3.61–3.67 V at 101.3 kPa (3.61–3.67 V at 1.01
kgf/cm
2, 3.61–3.67 V at 14.7 psi)
Intake air temperature sensor resistance 290–390  at 80 °C (290–390  176 °F)
Coolant temperature sensor resistance 2.51–2.78 k at 20 °C (2.51–2.78 k at 68 °F)
210–221  at 100 °C (210–221  at 212 °F)
Idling condition
Engine idling speed 1900–2100 r/min
CO% 3.0–4.0 % (USA) (CAN)
Intake vacuum 25.3–29.3 kPa (190–220 mmHg, 7.5–8.7 inHg)
(USA) (CAN)
Water temperature 70.0–90.0 °C (158.00–194.00 °F)
Oil temperature 70.0–80.0 °C (158.00–176.00 °F)
Throttle grip free play 3.0–5.0 mm (0.12–0.20 in)

TIGHTENING TORQUES
2-16
TIP
Exhaust pipe nut
First temporarily tighten nuts to 13 Nm (1.3 m·kgf, 9.4 ft·lbf). Then retighten them to 20 Nm (2.0 m·kgf,
14 ft·lbf).Clutch boss nut M16 1 75 Nm (7.5 m·kgf, 54 ft·lbf)Use a
lock
washer.
Drive sprocket nut M18 1 75 Nm (7.5 m·kgf, 54 ft·lbf)Use a
lock
washer.
Segment
M8 1 30 Nm (3.0 m·kgf, 22 ft·lbf)
Shift guide bolt
M6 2 10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Stopper lever bolt
M6 1 10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Shift pedal bolt M6 1 12 Nm (1.2 m·kgf, 8.7 ft·lbf)
Rotor nut
M12 1 65 Nm (6.5 m·kgf, 47 ft·lbf)
Stator screw
M5 2 7 Nm (0.7 m·kgf, 5.1 ft·lbf)
Crankshaft position sensor bolt
M6 2 10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Damper assembly cover bolt
M6 2 10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Starter clutch bolt
M6 6 16 Nm (1.6 m·kgf, 12 ft·lbf)
Starter motor bolt
M6 1 12 Nm (1.2 m·kgf, 8.7 ft·lbf)
Coolant temperature sensor
M10 1 16 Nm (1.6 m·kgf, 12 ft·lbf)
Neutral switch bolt
M5 2 3.5 Nm (0.35 m·kgf, 2.5 ft·lbf)
Intake air temperature sensor screw
M5 1 1.5 Nm (0.15 m·kgf, 1.1 ft·lbf)
Rectifier/regulator bolt
M6 2 7 Nm (0.7 m·kgf, 5.1 ft·lbf)
ECU bolt
M5 2 3.8 Nm (0.38 m·kgf, 2.8 ft·lbf)
Ignition coil bolt
M6 2 7 Nm (0.7 m·kgf, 5.1 ft·lbf)
Throttle position sensor screw
M5 2 3.4 Nm (0.34 m·kgf, 2.5 ft·lbf)
Intake air pressure sensor screw
M6 1 5 Nm (0.5 m·kgf, 3.6 ft·lbf) ITEMThread
sizeQ’ty TIGHTENING TORQUES Remarks
LT
LT
LT
LT
LT
LT

CABLE ROUTING DIAGRAM
2-38
1. Cable guide
2. Speed sensor lead
3. Joint coupler
4. Ground lead
5. Throttle position sensor lead
6. Throttle position sensor coupler
7. Radiator breather hose
8. Cylinder head breather hose
9. Crankcase breather hose
10. Radiator hose
11. Fuel hose
12. Engine ground lead
13. Coolant temperature sensor coupler
14. Radiator fan motor lead
15. Intake air pressure sensor coupler
16. Intake air temperature sensor coupler
17. Start switch coupler
18. Radiator fan motor coupler
19. Clutch switch coupler
20. Air filter case
21. Plate
22. Bracket
A. Pass the wire harness under the start switch lead
and clutch switch lead.
B. Insert and fix the joint coupler to the plate. After
fixing it, attach the cover.
C. Pass the throttle position sensor lead to the out-
side of the tension arm (the outside of the vehi-
cle).
D. After connecting the throttle position sensor cou-
pler, attach the cover.
E. Pass the radiator breather hose to the outside of
the tension arm and the throttle position sensor
lead (the outside of the vehicle), and to the inside
of the radiator hose (the side of the vehicle).
F. 45°
G. Install the engine ground lead within a range of
45° from a location where it will not run over the
step difference of the radiator hose joint. Both
sides of the engine ground lead terminal can be
used.
H. Attach the coupler cover to the coolant tempera-
ture sensor coupler.
I. Pass the radiator fan motor lead to the inside of
the tension arm (the side of the vehicle).
J. Install the ground lead terminal between the plate
and the bolt.
K. Fix the ground lead terminal to the detent in the
plate. For the ground lead terminal, either side
will do.
L. Detent

ENGINE REMOVAL
6-3
Removing the electronic parts
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
Seat Refer to “GENERAL CHASSIS” on page 5-1.
Side cover (left/right) Refer to “GENERAL CHASSIS” on page 5-1.
Air scoop (left / right) Refer to “GENERAL CHASSIS” on page 5-1.
Fuel tank Refer to “FUEL TANK” on page 8-1.
Air filter case cover
1 Rectifier/regulator 1
2ECU 1
3 Ignition coil 1
4 Neutral switch 1
5 AC magneto coupler 1 Disconnect.
6 Crankshaft position sensor coupler 1 Disconnect.
7 Coolant temperature sensor coupler 1 Disconnect.
For installation, reverse the removal proce-
dure.
T.R.
T.R.
T.R.T.R.
7 3
6
5
142
LT
New
LS

CYLINDER HEAD
6-18
EAS2GB2246
CYLINDER HEAD
Removing the cylinder head
Order Part name Q’ty Remarks
Seat Refer to “GENERAL CHASSIS” on page 5-1.
Side cover (left/right) Refer to “GENERAL CHASSIS” on page 5-1.
Air scoop (left / right) Refer to “GENERAL CHASSIS” on page 5-1.
Fuel tank Refer to “FUEL TANK” on page 8-1.
Exhaust pipe and silencer Refer to “ENGINE REMOVAL” on page 6-1.
Radiator hose Disconnect.
Coolant temperature sensor coupler Disconnect.
Throttle body Refer to “THROTTLE BODY” on page 8-7.
Camshaft Refer to “CAMSHAFT” on page 6-11.
Upper engine bracket Refer to “ENGINE REMOVAL” on page 6-1.
1 Nut (cylinder head) 2
2 Bolt (cylinder head) 4
3 Cylinder head 1
4 Cylinder head gasket 1
5 Timing chain guide (intake side) 1
6 Oil check bolt 1
6
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
33 Nm (3.3 m kgf, 24 ft Ibf)T.R.
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.

RADIATOR
7-2
4 Right radiator 1
5 Radiator hose 2 1
6 Radiator hose 3 1
7 Radiator hose 4 1
8 Radiator pipe 2 1
9 Radiator breather hose 1
10 Left radiator 1
11 Radiator hose 1 1
12 Radiator pipe 1 1
13 Coolant temperature sensor 1
For installation, reverse the removal proce-
dure.
Removing the radiator
Order Part name Q’ty Remarks
12
13
New
New
New
LS
LS
3
458 Nm (0.8 m kgf, 5.8 ft Ibf)T.R.
6
7
89
10
112
2
2
2 22 2
1
1