2001 YAMAHA YZ426F check oil

4 - 93
ENG

TRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H4801
Shift fork, shift cam and segment
1. Inspect:
l
Shift fork
1

Wear/damage/scratches
®
Replace.
2. Inspect:
l
Shift cam
1

l
Segment
2

Bend/wear/damage
®
Replace.
3. Check:
lShift fork movement
Unsmooth operation ® Replace shift
fork.
NOTE:
For a malfunctioning shift fork, replace not only
the shift fork itself but the two gears each adja-
cent to the shift fork.
ASSEMBLY AND INSTALLATION
Transmission
1. Install:
l5th pinion gear (21T) 1
l3rd pinion gear (18T) 2
lCollar 3
l4th pinion gear (22T) 4
l2nd pinion gear (15T) 5
To main axle 6.
NOTE:
lApply the molybdenum disulfide oil on the
4th and 5th pinion gears inner circumference
and on the end surface.
lApply the molybdenum disulfide oil on the
2nd and 3rd pinion gears inner circumfer-
ence.

4 - 95
ENG

TRANSMISSION, SHIFT CAM AND SHIFT FORK
5. Install:
l
Shift fork 1 (L)
1

l
Shift fork 2 (C)
2

l
Shift fork 3 (R)
3

l
Shift cam
4

To main axle and drive axle.
NOTE:

l
Apply the molybdenum disulfide oil on the
shift fork grooves.
l
Mesh the shift fork #1 (L) with the 4th wheel
gear
5
and #3 (R) with the 5th wheel gear
7
on the drive axle.
l
Mesh the shift fork #2 (C) with the 3rd pinion
gear
6
on the main axle.
6. Install:
l
Transmission assembly
1

To crankcase (left)
2
.
NOTE:

Apply the engine oil on the bearings and guide
bars.
7. Check:
l
Shifter operation
l
Transmission operation
Unsmooth operation
®
Repair.

5 - 35
CHASFRONT FORK
13. Check:
lInner tube smooth movement
Tightness/binding/rough spots ®
Repeat the steps 2 to 12.
14. Compress the front fork fully.
15. Fill:
lFront fork oil
Until outer tube top surface with recom-
mended fork oil 1.
ACHTUNG:CAUTION:
lBe sure to use recommended fork oil. If
other oils are used, they may have an
excessively adverse effect on the front
fork performance.
lNever allow foreign materials to enter the
front fork.
Recommended oil:
Suspension oil “01”
16. After filling, pump the damper rod 1
slowly up and down more than 10 times
to distribute the fork oil.
17. Fill:
lFront fork oil
Until outer tube top surface with recom-
mended fork oil once more.
18. After filling, pump the outer tube 1 slowly
up and down (about 200 mm (7.9 in)
stroke) to distribute the fork oil once
more.
NOTE:
Be careful not to excessive full stroke. A stroke
of 200 mm (7.9 in) or more will cause air to
enter. In this case, repeat the steps 15 to 18.

5 - 36
CHASFRONT FORK
19. Wait ten minutes until the air bubbles
have been removed from the front fork,
and the oil has dispense evenly in system
before setting recommended oil level.
NOTE:
Fill with the fork oil up to the top end of the
outer tube, or the fork oil will not spread over to
every part of the front forks, thus making it
impossible to obtain the correct level.
Be sure to fill with the fork oil up to the top of
the outer tube and bleed the front forks.
20. Measure:
lOil level (left and right) a
Out of specification ® Adjust.
NOTE:
Be sure to install the spring guide 2 when
checking the oil level.
WARNING
Never fail to make the oil level adjustment
between the maximum and minimum level
and always adjust each front fork to the
same setting. Uneven adjustment can
cause poor handling and loss of stability.
Standard oil level:
130 mm (5.12 in)
Extent of adjustment:
80 ~ 150 mm (3.15 ~ 5.91 in)
From top of outer tube with
inner tube and damper rod 1
fully compressed without
spring.

–+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 - 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)