2001 YAMAHA YZ426F oil

5 - 60
CHAS
EC583000
REMOVAL POINTS
EC583320
Bearing
1. Remove:
lStopper ring (upper bearing) 1
NOTE:
Press in the bearing while pressing its outer
race and remove the stopper ring.
2. Remove:
lUpper bearing 1
NOTE:
Remove the bearing by pressing its outer race.
3. Remove:
lLower bearing 1
NOTE:
Remove the bearing by pressing its outer race.
EC584000
INSPECTION
Rear shock absorber
1. Inspect:
lDamper rod 1
Bends/damage ® Replace absorber
assembly.
lShock absorber 2
Oil leaks ® Replace absorber assem-
bly.
Gas leaks ® Replace absorber assem-
bly.
lSpring 3
Damage ® Replace spring.
Fatigue ® Replace spring.
Move spring up and down.
lSpring guide 4
Wear/damage ® Replace spring guide.
lBearing 5
Free play exists/unsmooth revolution/
rust ® Replace.
REAR SHOCK ABSORBER

6 - 1
–+ELECELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC600000
ELECTRICAL
EC610000
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC611000
ELECTRICAL COMPONENTS
1“ENGINE STOP” button
2TPS (throttle position sensor)
3Neutral switch
4CDI magneto
5Ignition coil
6Spark plug
7CDI unitCOLOR CODE
B...................... Black
Br .................... Brown
G ..................... Green
L ...................... Blue
O ..................... Orange
P...................... Pink
R ..................... Red
EC612000
WIRING DIAGRAM
7
15
6
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

–+ELEC
6 - 2
MAP-CONTROLLED CDI UNIT
MAP-CONTROLLED CDI UNIT
A map-controlled, CDI ignition system is used in the YZ426F.
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
nFunction of Component
Component Function
TPS
(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 TPS and pickup coil sensor are analyzed by the
computer in the CDI unit, which then adjusts ignition timing for the
operation requirements.
nPrincipal 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:
lRemove the following parts before inspection.
1) Seat
2) Fuel tank
lUse the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket 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”
button.Replace.
Check ignition coil. Primary coil Replace.
Secondary coilReplace.
Check CDI magneto. Pick-up coil Replace.
Source 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

6 - 5
–+ELECIGNITION SYSTEM
EC626002
IGNITION COIL INSPECTION
1. Inspect:
lPrimary coil resistance
Out of specification ® Replace.
Tester (+) lead ® Orange lead 1
Tester (–) lead ® Black lead 2
Primary coil
resistanceTester selector
position
0.20 ~ 0.30 W at
20 ˚C (68 ˚F)W ´ 1
2. Inspect:
lSecondary coil resistance
Out of specification ® Replace.
NOTE:
When inspecting the secondary coil resis-
tance, remove the spark plug cap.
EC627011
CDI MAGNETO INSPECTION
1. Inspect:
lPick-up coil resistance
Out of specification ® Replace. Tester (+) lead ® Spark plug lead 1
Tester (–) lead ® Orange lead 2
Secondary coil
resistanceTester selector
position
9.5 ~ 14.3 kW at
20 ˚C (68 ˚F)kW ´ 1
Tester (+) lead ® Red lead 1
Tester (–) lead ® White lead 2
Pick-up coil
resistanceTester selector
position
248 ~ 372 W at
20 ˚C (68 ˚F)W ´ 100

6 - 6
–+ELECIGNITION SYSTEM
2. Inspect:
lSource coil 1 resistance
Out of specification ® Replace.
3. Inspect:
lSource coil 2 resistance
Out of specification ® Replace. Tester (+) lead ® Brown lead 1
Tester (–) lead ® Green lead 2
Source coil 1
resistanceTester selector
position
720 ~ 1,080 W
at 20 ˚C (68 ˚F)W ´ 100
Tester (+) lead ® Pink lead 1
Tester (–) lead ® Black lead 2
Source coil 2
resistanceTester selector
position
44 ~ 66 W at
20 ˚C (68 ˚F)W ´ 10
NEUTRAL SWITCH INSPECTION
1. Inspect:
lNeutral switch conduct
No continuity while in neutral ® Replace.
Continuity while in gear ® Replace.
EC628000
CDI UNIT INSPECTION
Check all electrical components. If no fault is
found, replace the CDI unit. Then check the
electrical components again.Tester (+) lead ® Sky blue lead 1
Tester (–) lead ® Ground
Sb
1GroundTester selec-
tor position
NEUTRALW ´ 1IN GEAR
–+ W´1
R/W
W Sb L/W
1

–+ELEC
6 - 7
TPS (THROTTLE POSITION SENSOR) SYSTEM
EC690000
TPS (THROTTLE POSITION SENSOR) SYSTEM
INSPECTION STEPS
If the TPS 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 TPS. TPS coil Replace.
*Check CDI magneto. Source coil Replace.
Check CDI unit.TPS input
voltageReplace.
OK
OK
OK
No good
No good
No good
No good

6 - 8
–+ELEC

TPS (THROTTLE POSITION SENSOR) SYSTEM
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
l
Couplers and leads connection
Rust/dust/looseness/short-circuit
®

Repair or replace.
TPS COIL INSPECTION
1. Inspect:
l
TPS coil resistance
Out of specification
®
Replace.
2. Loosen:
l
Throttle stop screw
NOTE:

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

TPS coil
resistanceTester selector
position
4 ~ 6 k
W
at
20 ˚C (68 ˚F)k
W

´
1
3. Inspect:
l
TPS 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

TPS coil variable
resistance
Tester selec-
tor position
Full closedFull opened
k
W

´
1 0 ~ 2 kW at
20 ˚C
(68 ˚F)4 ~ 6 kW at
20 ˚C
(68 ˚F)