Yamaha wr250f Application guide

5PH-28199-30
WR250F
(
N
)
OWNER’S SERVICE MANUAL
MANUEL D’ATELIER DU
ET PROPRIETAIRE
FAHRER- UND
WARTUNGS-HANDBUCH
MANUALE DI SERVIZIO DEL
PROPRIETARIO

3 - 10
INSP
ADJ
THROTTLE CABLE ADJUSTMENT
THROTTLE CABLE ADJUSTMENT
1. Check:
●Throttle grip free play a
Out of specification →Adjust.
Throttle grip free play a:
3 ~ 5 mm (0.12 ~ 0.20 in)
2. Adjust:
●Throttle grip free play
Throttle grip free play adjustment steps:
●Remove the throttle cable cap 1and
throttle cable cover 2.
N
OTE:
●Before adjusting the throttle cable free
play, the engine idle speed should be
adjusted.
●When the motorcycle is accelerating,
throttle cable #1 3is pulled and throttle
cable #2 4is pushed.
1st step:
●Loosen the locknuts 5on throttle cable
#2.
●Adjust the free play by changing their
tightening position.
2nd step:
●Loosen the locknuts 6on throttle cable
#1.
●Adjust the free play by changing their
tightening position.
●Tighten the locknuts.
WARNING
After adjusting, turn the handlebar to
right and left and make sure that the
engine idling does not run faster.
●Install the throttle cable cover and throttle
cable cap.
T
R
.
.
Throttle cable cover:
4 Nm (0.4 m • kg, 2.9 ft • lb)
2
1

3 - 11
INSP
ADJ
THROTTLE LUBRICATION/
DECOMPRESSION ADJUSTMENT
THROTTLE LUBRICATION
1. Remove:
●Rubber cover 1
●Throttle grip cap 2
2. Apply:
●Lithium soap base grease
On the throttle cable end a.
3. Install:
●Throttle grip cap
●Screw (throttle grip cap)
●Rubber cover
T
R
.
.
4 Nm (0.4 m · kg, 2.9 ft · lb)
DECOMPRESSION ADJUSTMENT
1. Check:
●Decompression lever free play a
Out of specification →Adjust.
Checking steps:
●Remove the timing mark accessing screw
1and crankshaft end accessing screw
2.
●Turn the crankshaft counterclockwise with
a wrench.
N
OTE:
Squeezing the decompression lever allows
the crankshaft to be turned easily.
●Align the T.D.C. mark bon the rotor with
the align mark con the crankcase cover
when piston is at T.D.C. on compression
stroke.
●Check the free play.
Free play a:
5 ~ 9 mm (0.20 ~ 0.35 in)

3 - 19
INSP
ADJ
ENGINE IDLING SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it
up.
2. Attach:
●Inductive tachometer
To spark plug lead.
3. Adjust:
●Engine idling speed
Adjustment steps:
●Adjust the pilot screw.
Refer to “PILOT SCREW ADJUSTMENT”
section.
●Turn the throttle stop screw 1until the
engine runs at the lowest possible speed.
To increase idle speed →
Turn the throttle stop screw 1in a.
To decrease idle speed →
Turn the throttle stop screw 1out b.
Inductive tachometer:
YU-08036-B
Engine tachometer:
90890-03113
Engine idling speed:
1,700 ~ 1,900 r/min
VALVE CLEARANCE INSPECTION AND
ADJUSTMENT
N
OTE:
●The valve clearance should be adjusted
when the engine is cool to the touch.
●The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
●Seat
●Fuel tank
Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section in the CHAP-
TER 4.
2. Drain:
●Coolant
Refer to “COOLANT REPLACEMENT”
section.
ENGINE IDLING SPEED ADJUSTMENT/
VALVE CLEARANCE INSPECTION AND ADJUSTMENT

4 - 7
ENG
CARBURETOR
CARBURETOR
Extent of removal: 1Carburetor removal
Extent of removal Order Part name Q’ty Remarks
CARBURETOR REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Clamp 2
2 Throttle position sensor lead cou-
pler 1
3 Throttle cable cover 1
4 Throttle cable 2
5 Throttle cable cap 1
6 Clamp (air filter joint) 1 Loosen the screw (air filter joint).
7 Clamp (carburetor joint) 2 Loosen the screws (carburetor joint).
8 Carburetor assembly 1
9 Carburetor joint 1
1

4 - 8
ENG
CARBURETOR
EC468000
CARBURETOR DISASSEMBLY
Extent of removal: 1Carburetor disassembly
Extent of removal Order Part name Q’ty Remarks
CARBURETOR DISASSEMBLY
1Carburetor breather hose 4
2Valve lever housing cover 1
3Screw (throttle shaft) 1
4Throttle valve 1
5Needle holder 1
6Jet needle 1
7Accelerator pump cover 1
8Spring 1
9Diaphragm (accelerator pump) 1
0Air cut valve cover 1
ASpring (air cut valve) 1
BDiaphragm (air cut valve) 1
CFloat chamber 1
DLeak jet 1
EPilot screw 1 Refer to “REMOVAL POINTS”.
FFloat pin 1
1

4 - 9
ENG
CARBURETOR
Extent of removal Order Part name Q’ty Remarks
GFloat 1
HNeedle valve 1
IValve seat 1
JMain jet 1
KNeedle jet 1
LSpacer 1
MPilot jet 1
NStarter jet 1
OPush rod 1 Pull the push rod.
PThrottle shaft assembly 1
QPush rod link lever assembly 1
RIntake joint 1
SPilot air jet 1
TMain air jet 1
UCold starter plunger 1
VHot starter plunger (red) 1
1

4 - 10
ENG
CARBURETOR
HANDLING NOTE
CAUTION:
Do not loosen the screws (throttle position
sensor) 1except when changing the throt-
tle position sensor due to failure because it
will cause a drop in engine performance.
REMOVAL POINTS
Pilot screw
1. Remove:
●Pilot screw 1
N
OTE:
To optimize the fuel flow at a small throttle
opening, each machine’s pilot screw has been
individually set at the factory. Before removing
the pilot screw, turn it in fully and count the
number of turns. Record this number as the
factory-set number of turns out.
INSPECTION
Carburetor
1. Inspect:
●Carburetor body
Contamination →Clean.
N
OTE:
●Use a petroleum based solvent for cleaning.
Blow out all passages and jets with com-
pressed air.
●Never use a wire.

4 - 11
ENG
CARBURETOR
2. Inspect:
●Main jet 1
●Pilot jet 2
●Needle jet 3
●Starter jet 4
●Main air jet 5
●Pilot air jet 6
●Leak jet 7
Damage →Replace.
Contamination →Clean.
N
OTE:
●Use a petroleum based solvent for cleaning.
Blow out all passages and jets with com-
pressed air.
●Never use a wire.
Needle valve
1. Inspect:
●Needle valve 1
●Valve seat 2
Grooved wear a→Replace.
Dust band c→Clean.
N
OTE:
Replace the needle valve and valve seat as a
set.
EC464301
Throttle valve
1. Check:
●Free movement
Stick →Repair or replace.
N
OTE:
Insert the throttle valve 1into the carburetor
body, and check for free movement.
EC464401
Jet needle
1. Inspect:
●Jet needle 1
Bends/wear →Replace.
●Clip groove
Free play exists/wear →Replace.
●Clip position
* For EUROPE
** For CDN, ZA, AUS and NZ
Standard clip position:
No.3 Groove
*,** No.4 Groove

4 - 12
ENG
CARBURETOR
Float height
1. Measure:
●Float height a
Out of specification →Adjust.
Float height:
8.0 mm (0.31 in)
Measurement and adjustment steps:
●Hold the carburetor in an upside down
position.
N
OTE:
●Slowly tilt the carburetor in the opposite
direction, then take the measurement
when the needle valve aligns with the float
arm.
●If the carburetor is level, the weight of the
float will push in the needle valve, result-
ing in an incorrect measurement.
●Measure the distance between the mating
surface of the float chamber and top of the
float using a vernier calipers.
N
OTE:
The float arm should be resting on the nee-
dle valve, but not compressing the needle
valve.
●If the float height is not within specifica-
tion, inspect the valve seat and needle
valve.
●If either is worn, replace them both.
●If both are fine, adjust the float height by
bending the float tab bon the float.
●Recheck the float height.
EC464600
Float
1. Inspect:
●Float 1
Damage →Replace.

4 - 13
ENG
Starter plunger
1. Inspect:
●Cold starter plunger 1
●Hot starter plunger (red) 2
Wear/damage →Replace.
Accelerator pump
1. Inspect:
●Diaphragm (accelerator pump) 1
●Spring (accelerator pump) 2
●Accelerator pump cover 3
●O-ring 4
●Push rod 5
Tears (diaphragm)/damage →Replace.
Dirt →Clean.
2. Inspect:
●Throttle shaft 1
●Spring 2
●Lever 1 3
●Spring 1 4
●Lever 2 5
●Spring 2 6
Dirt →Clean.
12
34
56
Air cut valve
1. Inspect:
●Diaphragm (air cut valve) 1
●Spring (air cut valve) 2
●Air cut valve cover 3
●O-ring 4
Tears (diaphragm)/damage →
Replace.
123
4
ASSEMBLY AND INSTALLATION
Carburetor
1. Install:
●Hot starter plunger (red) 1
●Cold starter plunger 2
CARBURETOR

4 - 14
ENG
CARBURETOR
2. Install:
●Main air jet 1
●Pilot air jet 2
●Intake joint 3
T
R
.
.
5 Nm (0.5 m · kg, 3.6 ft · lb)
3. Install:
●Spring 1 1
●Lever 1 2
To lever 2 3.
N
OTE:
Make sure the spring 1 fits on the stopper aof
the lever 2.
3
1
2
a
4. Install:
●Spring 2 1
To lever 2 2.
1
2
5. Install:
●Push rod link lever assembly 1
N
OTE:
Make sure the stopper aof the spring 2 fits
into the recess bin the carburetor.
1
a
b
6. Install:
●Washer 1
●Circlip 2
21

4 - 15
ENG
CARBURETOR
7. Install:
●Spring 1
●Joint collar 2
To throttle shaft 3.
N
OTE:
Install the bigger hook aof the spring fits on
the stopper bof the throttle shaft pulley.
8. Install:
●Throttle shaft assembly 1
●Washer (metal) 2
●Washer (resin) 3
●Valve lever 4
N
OTE:
●Apply the fluorochemical grease on the bear-
ings.
●Fit the projection aon the throttle shaft
assembly into the slot bin the throttle posi-
tion sensor.
●Make sure the stopper cof the spring fits
into the recess in the carburetor.
●Turn the throttle shaft assembly left while
holding down the lever 1 5and fit the throt-
tle stop screw tip dto the stopper eof the
throttle shaft assembly pulley.
a
b
1234
c
e
d
5
9. Install:
●Push rod 1
N
OTE:
While holding down the lever 1 2, insert the
push rod farthest into the carburetor.
1
2

4 - 16
ENG
CARBURETOR
10.Install:
●Starter jet 1
●Pilot jet 2
●Spacer 3
●Needle jet 4
●Main jet 5
11.Install:
●Valve seat
●Screw (valve seat) 1
●Needle valve 2
●Float 3
●Float pin 4
N
OTE:
●After installing the needle valve to the float,
install them to the carburetor.
●Check the float for smooth movement.
12.Install:
●Pilot screw 1
●Spring 2
●Washer 3
●O-ring 4
Note the following installation points:
●Turn in the pilot screw until it is lightly
seated.
●Turn out the pilot screw by the number of
turns recorded before removing.
Pilot screw:
1-3/4 turns out (example)
13.Install:
●O-ring
●Leak jet 1
●Float chamber 2
●Bolt (float chamber) 3
●Cable holder (throttle stop screw cable)
4
●Hose holder (carburetor breather hose)
5

4 - 17
ENG
CARBURETOR
14.Install:
●Diaphragm (air cut valve) 1
●Spring (air cut valve) 2
●O-ring 3
●Air cut valve cover 4
●Screw (air cut valve cover) 5

1
2
3

5
4
15.Install:
●Diaphragm (accelerator pump) 1
●Spring 2
●O-ring 3
●Accelerator pump cover 4
●Bolt (accelerator pump cover) 5
N
OTE:
Install the diaphragm (accelerator pump) with
its mark afacing the spring.
16.Install:
●Jet needle 1
●Collar 2
●Spring 3
●Needle holder 4
●Throttle valve plate 5
To throttle valve 6.
5
6
1
23
4
17.Install:
●Throttle valve assembly 1
●Screw (throttle shaft) 2
N
OTE:
Install the valve lever rollers 3into the slits a
of the throttle valve.
18.Install:
●O-ring 1
●Valve lever housing cover 2
●Bolt (valve lever housing cover) 3

4 - 18
ENG
CARBURETOR
19.Install:
●Carburetor breather hose 1
N
OTE:
Install the carburetor breather hoses to the
carburetor so that the hoses do not bend near
where they are installed.
Carburetor installation
1. Install:
●Clamp 1
N
OTE:
Install the projections aon the carburetor joint
between the clamp ends.
aa
1
1
2. Install:
●Carburetor joint 1
N
OTE:
Install the projection aon the cylinder head
between the carburetor joint slots b.
T
R
.
.
3 Nm (0.3 m · kg, 2.2 ft · lb)
3. Install:
●Carburetor 1
N
OTE:
Install the projection between the carburetor
joint slots.
1
4. Tighten:
●Screw (air filter joint) 1
●Screw (carburetor joint) 2
1
2
T
R
.
.
3 Nm (0.3 m · kg, 2.2 ft · lb)
T
R
.
.
3 Nm (0.3 m · kg, 2.2 ft · lb)

4 - 19
ENG
5. Install:
●Throttle cable cap 1
1
6. Install:
●Throttle cable 1
7. Adjust:
●Throttle grip free play
Refer to “THROTTLE CABLE ADJUST-
MENT” section in the CHAPTER 3.
8. Install:
●Throttle cable cover 1
●Screw (throttle cable cover) 2
N
OTE:
Install the throttle cable cover with its pawl a
hung on the carburetor.
12
a
T
R
.
.
4 Nm (0.4 m · kg, 2.9 ft · lb)
9. Install:
●Throttle position sensor lead coupler 1
●Clamp 2
Refer to “CABLE ROUTING DIA-
GRAM” section in the CHAPTER 2.
10.Install:
●Clamp 1
Refer to “CABLE ROUTING DIA-
GRAM” section in the CHAPTER 2.
1
CARBURETOR

–+
ELEC
6 - 7
THROTTLE POSITION SENSOR SYSTEM
THROTTLE POSITION SENSOR SYSTEM
INSPECTION STEPS
If the throttle position sensor will not operate, use the following inspection steps.
*marked: Refer to “IGNITION SYSTEM” section.
N
OTE:
●Remove the following parts before inspection.
1) Seat
2) Fuel tank
●Use the following special tools in this inspection.
Pocket tester:
YU-3112-C/90890-03112 Inductive tachometer: YU-08036-B
Engine tachometer:
90890-03113
Check entire ignition
system for connection. Repair or replace.
Check throttle position
sensor. Throttle posi- tion sensor coil Replace.
*Check CDI magneto. Charging coil Replace.
Check CDI unit. Throttle posi- tion sensor
input voltage Replace.
OK
OK
OK
No good
No good
No good
No good

6 - 8
–+
ELEC
THROTTLE POSITION SENSOR SYSTEM
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
●Couplers and leads connection
Rust/dust/looseness/short-circuit →
Repair or replace.
THROTTLE POSITION SENSOR COIL
INSPECTION
1. Inspect:
●Throttle position sensor coil resistance
Out of specification →Replace.
2. Loosen:
●Throttle stop screw 1
N
OTE:
Turn out the throttle stop screw until the throt-
tle shaft is in the full close position.
Tester (+) lead →Blue lead 1
Tester (–) lead →Black lead 2
Throttle posi-
tion sensor coil
resistance
Testerselector
position
4 ~ 6 kΩat
20 ˚C (68 ˚F) kΩ×1
3. Inspect:
●Throttle position sensor coil variable
resistance
Check that the resistance in increased
as the throttle grip is moved from the
full close position to the full open posi-
tion.
Out of specification →Replace.
Tester (+) lead →Yellow lead 1
Tester (–) lead →Black lead 2
Throttle position sen-
sor coil variable
resistance
Tester
selector
position
Full closed Full opened
kΩ×1
Zero~3kΩ
at 20 ˚C
(68 ˚F)
4 ~ 6 kΩat
20 ˚C
(68 ˚F)

6 - 9
–+
ELEC
THROTTLE POSITION SENSOR SYSTEM
THROTTLE POSITION SENSOR
REPLACEMENT AND ADJUSTMENT
1. Remove:
●Throttle position sensor coupler
●Screw (throttle position sensor) 1
●Washer 2
●Throttle position sensor 3
N
OTE:
Loosen the screws (throttle position sensor)
using the T20 bit (tamper resistant fastener
type).
2. Replace:
●Throttle position sensor
3. Install:
●Throttle position sensor 1
●Washer 2
●Screw (throttle position sensor) 3
N
OTE:
●Align the slot ain the throttle position sen-
sor with the projection bon the carburetor.
●Temporarily tighten the screws (throttle posi-
tion sensor).
4. Adjust:
●Engine idling speed
Refer to “ENGINE IDLE SPEED
ADJUSTMENT” section in the CHAP-
TER 3.
5. Calculate:
●Throttle position sensor coil resistance
at idle speed
<Example>
If the throttle position sensor coil resistance is
5 kΩ, then the throttle position sensor coil
resistance at idle speed is:
5 kΩ×(0.13 ~ 0.15) = 650 ~ 750 Ω
Refer to “THROTTLE POSITION SEN-
SOR COIL INSPECTION” section
about the throttle position sensor coil
resistance.
Throttle position sensor coil resistance
at idle speed:
Throttle position sensor coil resis-
tance ×(0.13 ~ 0.15)