2003 YAMAHA YZ250F oil

5 - 53
CHASSWINGARM
EC574310
Connecting rod
1. Inspect:
Bearing (polylube bearing) 1
Collar 2
Free play exists/unsmooth revolution/rust
→ Replace bearing and collar as a set.
2. Inspect:
Bearing (polylube bearing) 1
Loss of solid lubrication → Replace.
Oil seal 3
Damage → Replace.
NOTE:
Polylube bearings, with solid lubrication, have
been adopted with the intent to make the nee-
dle bearings, used in this model, maintenance
free. With polylube bearings, no grease nipple
and regular lubrication is necessary. However,
grease should be applied to all oil seals and
collars when removed or installed.
EC575000
ASSEMBLY AND INSTALLATION
EC575201
Bearing and oil seal
1. Install:
Bearing 1
Oil seal 2
To swingarm.
NOTE:
Apply the molybdenum disulfide grease on
the bearing when installing.
Install the bearing by pressing it on the side
having the manufacture’s marks or numbers.
First install the outer and then the inner bear-
ings to a specified depth from inside.
Installed depth of bearings:
Outer a: Zero mm (Zero in)
Inner b: 8.5 mm (0.33 in)

5 - 54
CHASSWINGARM
2. Install:
Bearing 1
Oil seal 2
To relay arm.
NOTE:
Apply the molybdenum disulfide grease on
the bearing when installing.
Install the bearing by pressing it on the side
having the manufacture’s marks or numbers.
3. Install:
Bearing 1
Oil seal 2
To connecting rod.
NOTE:
Apply the molybdenum disulfide grease on
the bearing when installing.
Install the bearing by pressing it on the side
having the manufacture’s marks or numbers.
Installed depth of bearings a:
5 mm (0.20 in)
Installed depth of bearings a:
5 mm (0.20 in)
Swingarm
1. Install:
Bushing 1
Thrust bearing 2
Oil seal 3
Collar 4
To swingarm 5.
NOTE:
Apply the molybdenum disulfide grease on the
bushings, thrust bearings and oil seal lips.
2. Install:
Collar 1
To relay arm 2.
NOTE:
Apply the molybdenum disulfide grease on the
collars and oil seal lips.

5 - 55
CHASSWINGARM
3. Install:
Collar 1
To connecting rod 2.
NOTE:
Apply the molybdenum disulfide grease on the
collar and oil seal lips.
4. Install:
Connecting rod 1
Bolt (connecting rod) 2
Washer 3
Nut (connecting rod) 4
To relay arm 5.
NOTE:
Apply the molybdenum disulfide grease on the
bolt.
5. Install:
Relay arm 1
Bolt (relay arm) 2
Washer 3
Nut (relay arm) 4
To swingarm.
NOTE:
Apply the molybdenum disulfide grease on
the bolt.
Do not tighten the nut yet.
6. Install:
Swingarm 1
Pivot shaft 2
NOTE:
Apply the molybdenum disulfide grease on
the pivot shaft.
Insert the pivot shaft from right side.
7. Check:
Swingarm side play a
Free play exists → Replace thrust bear-
ing.
Swingarm up and down movement b
Unsmooth movement/binding/rough
spots → Grease or replace bearings,
bushings and collars.
T R..80 Nm (8.0 m · kg, 58 ft · lb)
T R..85 Nm (8.5 m · kg, 61 ft · lb)

5 - 60
CHAS
HANDLING NOTE
WARNING
This rear shock absorber is provided with a
separate type tank filled with high-pressure
nitrogen gas. To prevent the danger of
explosion, read and understand the follow-
ing information before handling the shock
absorber.
The manufacturer can not be held respon-
sible for property damage or personal
injury that may result from improper han-
dling.
1. Never tamper or attempt to disassem-
ble the cylinder or the tank.
2. Never throw the rear shock absorber
into an open flame or other high heat.
The rear shock absorber may explode
as a result of nitrogen gas expansion
and/or damage to the hose.
3. Be careful not to damage any part of
the gas tank. A damaged gas tank will
impair the damping performance or
cause a malfunction.
4. Take care not to scratch the contact
surface of the piston rod with the cylin-
der; or oil could leak out.
5. Never attempt to remove the plug at
the bottom of the nitrogen gas tank. It
is very dangerous to remove the plug.
6. When scrapping the rear shock
absorber, follow the instructions on
disposal.
NOTES ON DISPOSAL (YAMAHA DEALERS
ONLY)
Before disposing the rear shock absorber, be
sure to extract the nitrogen gas from valve 1.
Wear eye protection to prevent eye damage
from escaping gas and/or metal chips.
WARNING
To dispose of a damaged or worn-out rear
shock absorber, take the unit to your
Yamaha dealer for this disposal procedure.
REAR SHOCK ABSORBER

5 - 61
CHAS
EC583000
REMOVAL POINTS
EC583320
Bearing
1. Remove:
Stopper ring (upper bearing) 1
NOTE:
Press in the bearing while pressing its outer
race and remove the stopper ring.
2. Remove:
Upper bearing 1
NOTE:
Remove the bearing by pressing its outer race.
3. Remove:
Lower bearing 1
NOTE:
Remove the bearing by pressing its outer race.
EC584000
INSPECTION
Rear shock absorber
1. Inspect:
Damper rod 1
Bends/damage → Replace rear shock
absorber assembly.
Shock absorber 2
Oil leaks → Replace rear shock
absorber assembly.
Gas leaks → Replace rear shock
absorber assembly.
Spring 3
Damage → Replace spring.
Fatigue → Replace spring.
Move spring up and down.
Spring guide 4
Wear/damage → Replace spring guide.
Bearing 5
Free play exists/unsmooth revolution/
rust → Replace.
REAR SHOCK ABSORBER

6 - 1
–+ELEC

ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC600000
ELECTRICAL
EC610000
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC611000
ELECTRICAL COMPONENTS
1
Engine stop switch
2
Throttle position sensor
3
Neutral switch
4
CDI magneto
5
Spark plug
6
Ignition coil
7
CDI unit
COLOR CODE
B...................... Black
Br .................... Brown
G ..................... Green
L ...................... Blue
O ..................... Orange
P...................... Pink
R ..................... Red
Sb.................... Sky blue
EC612000
WIRING DIAGRAM
71
5
62
3
4
B/WB/W
B/L
B/Y
SbSb
G/B
LYLY
P
B
B
B
B
G
O
WR
P
GW
R PP
B Br W
W
B/YGBr
G RR
OB Sb Sb Y
Y
WY
W
GG
B
PP
Br BrR R
OL
B SbY LL
B/L B/WB/W G/B
B B
B/L L Sb
B/L
G/B G/B
B/Y
B/Y B/W
O B/W
BrBr

W ..................... White
Y ...................... Yellow
B/L ................... Black/Blue
B/W .................. Black/White
B/Y ................... Black/Yellow
G/B................... Green/Black
L/W .................. Blue/White
R/W .................. Red/White

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6 - 2
MAP-CONTROLLED CDI UNIT
MAP-CONTROLLED CDI UNIT
A map-controlled, CDI ignition system is used in the YZ250F.
The microcomputer in the CDI unit detects the engine speed and throttle position, thus determining
the optimum ignition timing through the entire operating range. In this way, quick throttle response
can be achieved according to various riding conditions.
CDI unit
Throttle position sensor
Pickup coil CDI magneto rotorIgnition coil


Function of Component

Component Function
Throttle position sensor Detects throttle valve opening and inputs it into the computer in the
CDI unit as a throttle opening signal.
Pickup coil Detects signal rotor revolutions and inputs them into the computer in
the CDI unit as engine revolution signals.
CDI unit The signals of the throttle position sensor and pickup coil sensor are
analyzed by the computer in the CDI unit, which then adjusts ignition
timing for the operation requirements.

Principal of 3-Dimensional Control
Conventionally, ignition timing was controlled only
by engine revolutions (2-dimensional control).
However, ignition timing needs advancement also
by engine load. Thus, accurate ignition timing can
be determined by adding throttle opening to deter-
mine ignition timing (3-dimensional control).
3-D Image Map of Ignition Timing
(different from actual characteristics)
Revolutions
Ignition timing
Throttle opening

–+ELEC

6 - 3
IGNITION SYSTEM
EC620000
IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
*marked: Only when the ignition checker is used.
NOTE:


Remove the following parts before inspection.
1) Seat
2) Fuel tank

Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754
Pocket tester:
YU-3112-C/90890-03112
Spark gap test*Clean or replace
spark plug.
Check entire ignition
system for connection.
(couplers, leads and
ignition coil)Repair or replace.
Check engine stop switch. Replace.
Check ignition coil. Primary coil Replace.
Secondary coil Replace.
Check CDI magneto. Pickup coil Replace.
Charging coil Replace.
Check neutral switch. Repair or replace.
Replace CDI unit.
No spark
OK
OK
OK
OK
OK
Spark
No good
No good
No good
No good
No good
No good
No good