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.