2017 YAMAHA WR 250F ECU

SWINGARM
5-66
EAS2GBB217REMOVING THE SWINGARM
1. Use a suitable stand to raise the rear wheel
off the ground.
EWA
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Measure:
• Swingarm side play
• Swingarm vertical movement
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the tightening torque of the pivot
shaft nut.
b. Measure the swingarm side play “a” by mov-
ing the swingarm from side to side.
c. If the swingarm side play is out of specifica-
tion, check the spacers, the bearings, and
the collars.
d. Check the swingarm vertical movement “b”
by moving the swingarm up and down.
If swingarm vertical movement is not smooth
or if there is binding, check the spacers, the
bearings, and the collars.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS2GBB218REMOVING THE BEARING
1. Remove:
• Bearing “1”
TIP
Remove the bearing by pressing its outer race.
EAS2GBB219CHECKING THE SWINGARM
1. Check:
• Swingarm
Bends/cracks/damage  Replace.
2. Check:
• Pivot shaft
Roll the pivot shaft on a flat surface.
Bends  Replace.
EWA
WARNING
Do not attempt to straighten a bent pivot
shaft.
3. Wash with kerosene:
• Pivot shaft
• Spacers
•Collars
• Bearing
4. Check:
• Oil seals
Damage  Replace.
• Bearing
• Spacers
Free play exists/unsmooth revolution/rust 
Replace bearing and bushing as a set. Pivot shaft nut
85 Nm (8.5 m·kgf, 61 ft·lbf)
Swingarm end free play limit (ra-
dial)
1.0 mm (0.04 in)
T R..

CHAIN DRIVE
5-69
EAS23420REMOVING THE DRIVE CHAIN
1. Stand the vehicle on a level surface.
EWA
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
TIP
Place the vehicle on a suitable stand so that the
rear wheel is elevated.
2. Remove:
•Drive chain
TIP
Cut the drive chain with the drive chain cut &
rivet tool. (Use goods on the market)
EAS23441CHECKING THE DRIVE CHAIN
1. Measure:
• 15-link section of the drive chain
Out of specification  Replace the drive
chain.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the length “a” between the inner
sides of the pins and the length “b” between
the outer sides of the pins on a 15-link sec-
tion of the drive chain as shown in the illus-
tration.
b. Calculate the length “c” of the 15-link section
of the drive chain using the following formu-
la.
Drive chain 15-link section length “c” =
(length “a” between pin inner sides + length
“b” between pin outer sides)/2
TIP
• When measuring a 15-link section of the drive
chain, make sure that the drive chain is taut.
• Perform this procedure 2–3 times, at a differ-
ent location each time.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
2. Check:
•Drive chain
Stiffness  Clean, lubricate, or replace.
3. Clean:
•Drive chain
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Wipe the drive chain with a clean cloth.
b. Put the drive chain in kerosene and remove
any remaining dirt.
c. Remove the drive chain from the kerosene
and completely dry it. 15-link length limit
239.3 mm (9.42 in)

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

FUEL TANK
8-5
2. Connect:
• Fuel hose
ECA
NOTICE
• Connect the fuel hose securely, and check
that the orientation of the installed fuel
hose holder is correct.
• Take care not to kink or pinch the fuel
hose.
TIP
• Insert the fuel hose into the fuel pipe securely
until you hear a “click”.
• Slide the fuel hose connector cover “1” at the
hose end in the direction of the arrow.
• Install the fuel hose connector holder “a”.
• Check that the fuel hose and the fuel pump
lead are routed through the guide on the cov-
er.
3. Connect:
• Fuel pump coupler
4. Install:
• Air scoop (left/right)
• Seat
• Side cover (left/right)
Refer to “GENERAL CHASSIS” on page 5-
1.
EAS2GBB348CHECKING THE FUEL PRESSURE
1. Check:
• Fuel pressure
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the side cover (left/right), the seat
and the air scoop (left/right).
Refer to “GENERAL CHASSIS” on page 5-
1.
b. Remove the fuel tank bolt and lift the fuel
tank.
c. Disconnect the fuel hose from the fuel
pump.
Refer to “REMOVING THE FUEL TANK” on
page 8-3.
EWA
WARNING
Cover the fuel hose connection with a cloth
when disconnecting it. This is because re-
sidual pressure in the fuel hose could cause
fuel to spurt out when the hose is removed.
ECA
NOTICE
Make sure that the fuel hose is disconnect-
ed by hand. Do not forcibly disconnect the
hose with tools.
d. Connect the pressure gauge “1” and the fuel
pressure adapter “2” to the fuel hose.
e. Start the engine.
f. Measure the fuel pressure.
Out of specification  Replace the fuel
pump.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
1
a
Pressure gauge
90890-03153
Pressure gauge
YU-03153
Fuel pressure adapter
90890-03186
Fuel pressure adapter
YM-03186
Fuel line pressure (at idle)
300.0–390.0 kPa (3.00–3.90
kgf/cm
2, 43.5–56.6 psi)
1
2

THROTTLE BODY
8-7
EAS2GBB351
THROTTLE BODY
Removing the throttle body
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.
ECU Refer to “ENGINE REMOVAL” on page 6-1.
Ignition coil Refer to “ENGINE REMOVAL” on page 6-1.
1 Intake air temperature sensor coupler 1 Disconnect.
2 Breather hose 3 1
3 Air filter case 1
4 Fuel injector coupler 1 Disconnect.
5 Intake air pressure sensor coupler 1 Disconnect.
6 Throttle position sensor coupler 1 Disconnect.
7 Throttle cable cover 1
8 Throttle cable 2
3
1
2
7
11
12
10
9
4
8
6
5
3.5 Nm (0.35 m kgf, 2.5 ft Ibf)T.R.
3.5 Nm (0.35 m kgf, 2.5 ft Ibf)T.R.
7 Nm (0.7 m kgf, 5.1 ft Ibf)T.R.
3.0 Nm (0.30 m kgf, 2.2 ft Ibf)T.R.
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.

9
ELECTRICAL SYSTEM
IGNITION SYSTEM.......................................................................................... 9-2
CIRCUIT DIAGRAM ................................................................................... 9-2
TROUBLESHOOTING ............................................................................... 9-4
ELECTRIC STARTING SYSTEM..................................................................... 9-6
CIRCUIT DIAGRAM ................................................................................... 9-6
STARTING CIRCUIT CUT-OFF SYSTEM OPERATION ........................... 9-8
TROUBLESHOOTING ............................................................................. 9-10
CHARGING SYSTEM..................................................................................... 9-12
CIRCUIT DIAGRAM ................................................................................. 9-12
TROUBLESHOOTING ............................................................................. 9-14
LIGHTING SYSTEM....................................................................................... 9-16
CIRCUIT DIAGRAM ................................................................................. 9-16
TROUBLESHOOTING ............................................................................. 9-18
SIGNALING SYSTEM.................................................................................... 9-20
CIRCUIT DIAGRAM ................................................................................. 9-20
TROUBLESHOOTING ............................................................................. 9-22
COOLING SYSTEM........................................................................................ 9-24
CIRCUIT DIAGRAM ................................................................................. 9-24
TROUBLESHOOTING ............................................................................. 9-26
FUEL INJECTION SYSTEM........................................................................... 9-28
CIRCUIT DIAGRAM ................................................................................. 9-28
ECU SELF-DIAGNOSTIC FUNCTION ..................................................... 9-30
TROUBLESHOOTING METHOD ............................................................. 9-31
YAMAHA DIAGNOSTIC TOOL ................................................................ 9-32
TROUBLESHOOTING DETAILS ............................................................. 9-35
FUEL PUMP SYSTEM.................................................................................... 9-56
CIRCUIT DIAGRAM ................................................................................. 9-56
TROUBLESHOOTING ............................................................................. 9-58

IGNITION SYSTEM
9-3
1. Joint connector
2. Joint connector
4. AC magneto
9. Battery
10.Frame ground
11.Starter relay
12.Main fuse
22.ECU (engine control unit)
23.Ignition coil
24.Spark plug
30.Joint connector
35.Lean angle sensor
36.Engine stop switch
48.Frame ground
49.Ignition coil sub-lead

IGNITION SYSTEM
9-5
8. Check the lean angle sensor.
Refer to “CHECKING THE LEAN
ANGLE SENSOR” on page 9-75.NG 
Replace the lean angle sensor.
OK 
9. Check the entire ignition system’s
wiring.
Refer to “CIRCUIT DIAGRAM” on
page 9-2.NG 
Properly connect or repair the ignition sys-
tem’s wiring.
OK 
Replace the ECU.