engine oil YAMAHA YZ250F 2001 Workshop Manual

5 - 2
CHAS

EC598100
REAR WHEEL
Extent of removal:
1
Rear wheel removal
2
Wheel bearing removal
3
Brake disc removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removal
REAR WHEEL REMOVAL
Hold the machine by placing the
suitable stand under the engine.
WARNING

Support the machine securely so there is no
danger of it falling over.
1 Nut (rear wheel axle) 1
2 Rear wheel axle 1
3 Drive chain puller 2
4 Rear wheel 1 Refer to “REMOVAL POINTS”.
5 Collar 2
6 Rear wheel sprocket 1
7 Oil seal 2
8 Circlip 1
9 Bearing 2 Refer to “REMOVAL POINTS”.
10Brake disc
1
2
31
3

FRONT WHEEL AND REAR WHEEL

6 - 1
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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
EC612000
WIRING DIAGRAM
7
16
5
2 3 4
LY
BYL
B/LL
G
P
W
R
Y
B
G
BR PBrWG
RB Br WP
R/W WL/W SbW R/W Sb L/WY
B/LL Sb B OY
LB/L B OSbSb
L/WR/W
WSb
B/L
B/WB/W
B/WB/W
Br
BB
LBBY
O

Sb .................... Sky blue
W ..................... White
Y ...................... Yellow
B/L ................... Black/Blue
B/W .................. Black/White
L/W .................. Blue/White
R/W .................. Red/White





6

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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

n
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.
n
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

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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:

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

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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.
NOTE:
lRemove the following parts before inspection.
1) Seat
2) Fuel tank
lUse the following special tools in this inspection.
Pocket tester:
YU-3112-C/90890-03112Inductive 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 coilReplace.
*Check CDI magneto. Charging coil Replace.
Check CDI unit.Throttle posi-
tion sensor
input voltageReplace.
OK
OK
OK
No good
No good
No good
No good

6 - 9
–+ELECTHROTTLE POSITION SENSOR SYSTEM
THROTTLE POSITION SENSOR
REPLACEMENT AND ADJUSTMENT
1. Remove:
lThrottle position sensor coupler
lScrew (throttle position sensor) 1
lWasher 2
lThrottle position sensor 3
NOTE:
Loosen the screws (throttle position sensor)
using the T20 bit (tamper resistant fastener
type).
2. Replace:
lThrottle position sensor
3. Install:
lThrottle position sensor 1
lWasher 2
lScrew (throttle position sensor) 3
NOTE:
lAlign the slot a in the throttle position sen-
sor with the projection b on the carburetor.
lTemporarily tighten the screws (throttle posi-
tion sensor).
4. Adjust:
lEngine idling speed
Refer to “ENGINE IDLE SPEED
ADJUSTMENT” section in the CHAP-
TER 3.
5. Calculate:
lThrottle position sensor coil resistance
at idle speed

If the throttle position sensor coil resistance is
5 kW, then the throttle position sensor coil
resistance at idle speed is:
5 kW ´ (0.13 ~ 0.15) = 650 ~ 750 W
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)

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–+ELECTHROTTLE POSITION SENSOR SYSTEM
6. Adjust:
lThrottle position sensor coil resistance
at idle speed
Adjustment steps:
Adjust the angle of the throttle position sen-
sor 1 to obtain the resistance calculated
(example: 650 ~ 750 W)
Tester (+) lead ® Yellow lead 2
Tester (–) lead ® Black lead 3
7. Tighten:
lScrew (throttle position sensor) 1
NOTE:
Tighten the screws (throttle position sensor)
using the T20 bit (tamper resistant fastener
type).
8. Install:
lThrottle position sensor coupler
THROTTLE POSITION SENSOR INPUT
VOLTAGE INSPECTION
1. Disconnect the throttle position sensor
coupler.
2. Start the engine.
3. Inspect:
lThrottle position sensor input voltage
Out of specification ® Replace the CDI
unit.
Tester (+) lead ® Blue lead 1
Tester (–) lead ® Black/Blue lead 2
Throttle posi-
tion sensor
input voltageTester selector
position
4 ~ 6 V DCV-20