2001 YAMAHA YZ426F engine

4 - 56
ENG
OIL FILTER, WATER PUMP AND CRANKCASE COVER
(RIGHT)
EC4G5220
Impeller shaft
1. Install:
lImpeller shaft 1
lPlain washer 2
lImpeller 3
NOTE:
lTake care so that the oil seal lip is not dam-
aged or the spring does not slip off its posi-
tion.
lWhen installing the impeller shaft, apply the
engine oil on the oil seal lip, bearing and
impeller shaft. And install the shaft while
turning it.
lHold the impeller shaft on its width across
the flats a with spanners, etc. and remove
the impeller.
T R..14 Nm (1.4 m · kg, 10 ft · lb)
Crankcase cover (right)
1. Install:
lDowel pin 1
lO-ring 2
lCollar 3
lGasket 4 New
2. Install:
lCrankcase cover (right) 1
lBolt
NOTE:
lApply the engine oil on the impeller shaft
end.
lWhen installing the crankcase cover onto the
crankcase, be sure that the impeller shaft
end 2 aligns with the balancer end slot 3.
lTighten the bolts in stage, using a crisscross
pattern.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

4 - 61
ENG

BALANCER
ASSEMBLY AND INSTALLATION
Balancer, balancer drive gear and balancer
driven gear
1. Install:
l
Balancer
1

NOTE:

When installing the balancer shaft, align the
center of the balancer shaft weight
a
along
the line connecting the centers of the crank-
shaft and balancer shaft.
2. Install:
l
Balancer driven gear
1

NOTE:

Install the balancer driven gear onto the bal-
ancer while aligning the punch mark
a
on the
balancer driven gear with the cut
b
in the bal-
ancer end.
3. Install:
l
Balancer drive gear
1

NOTE:

l
Align the punched mark
a
on the balancer
drive gear with the punched mark
b
on the
balancer driven gear.
l
Align the punched mark
c
on the balancer
drive gear with the lower spline
d
on the
crankshaft.
4. Install:
l
Lock washer
1

l
Nut (balancer)
2

l
Primary drive gear
3

l
Nut (primary drive gear)
4

NOTE:

l
Install the primary drive gear with its stepped
side
b
facing the engine.
l
Place an aluminum plate
a
between the
teeth of the balancer drive gear
5
and
driven gear
6
.
5. Bend the lock washer tab.
T R..50 Nm (5.0 m · kg, 3.6 ft · lb)
T R..75 Nm (7.5 m · kg, 54 ft · lb)
b3

4 - 64
ENG

OIL PUMP
INSPECTION
Oil pump
1. Inspect:
l
Oil pump drive gear
l
Oil pump driven gear
l
Rotor housing
l
Oil pump cover
Cracks/wear/damage
®
Replace.
2. Measure:
l
Tip clearance
a

Between the inner rotor
1
and the
outer rotor
2
.
l
Tip clearance
b

Between the outer rotor
2
and the rotor
housing
3
.
Out of specification
®
Replace the oil
pump.
Tip clearance
a
:
0.12 mm or less
(0.0047 in or less)
: 0.20 mm (0.006 in)
Tip clearance
b
:
0.09 ~ 0.17 mm (0.0035 ~ 0.0067 in)
: 0.24 mm (0.009 in)
Side clearance
c
:
0.03 ~ 0.10 mm (0.0012 ~ 0.0039 in)
: 0.17 mm (0.007 in)
3. Check:
l
Unsmooth
®
Repeat steps #1 and #2
or replace the defective parts.
ASSEMBLY AND INSTALLATION
Oil pump
1. Install:
l
Oil pump drive shaft
1
lWasher 2
lPin 3
lInner rotor 1 4
NOTE:
lApply the engine oil on the oil pump drive
shaft and inner rotor 1.
lFit the pin into the groove in the inner rotor 1.

4 - 65
ENGOIL PUMP
2. Install:
lOuter rotor 1 1
NOTE:
Apply the engine oil on the outer rotor 1.
3. Install:
lOil pump cover 1
lScrew (oil pump cover) 2
lPin 3
lInner rotor 2 4
lCirclip 5
NOTE:
lApply the lithium soap base grease on the oil
pump drive shaft end and inner rotor 2.
lFit the pin into the groove in the inner rotor 2.
4. Install:
lOuter rotor 2 1
lDowel pin 2
lOil pump assembly 3
lBolt (oil pump assembly)
[L = 30 mm (1.18 in)] 4
lBolt (oil pump assembly)
[L = 25 mm (0.98 in)] 5
NOTE:
Apply the lithium soap base grease on the
outer rotor 2.
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
5. Install:
lOil pump drive gear 1
lPlate washer 2
lCirclip 3
NOTE:
Apply the engine oil on the oil pump drive gear
inner circumference.
New

4 - 70
ENGKICK AXLE AND SHIFT SHAFT
EC4B5111
Stopper lever
1. Install:
lTorsion spring 1
lStopper lever 2
lBolt (stopper lever) 3
NOTE:
Align the stopper lever roller with the slot on
segment.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
Shift guide and shift lever assembly
1. Install:
lSpring 1
lPawl pin 2
lPawl 3
To shift lever 4.
NOTE:
Apply the engine oil on the springs, pawl pins
and pawls.
2. Install:
lShift lever assembly 1
To shift guide 2.2
1
3. Install:
lShift lever assembly 1
lShift guide 2
NOTE:
lThe shift lever assembly is installed at the
same time as the shift guide.
lApply the engine oil on the bolt (segment)
shaft.

4 - 71
ENGKICK AXLE AND SHIFT SHAFT
4. Install:
lBolt (shift guide) 1
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
EC4C5301
Shift shaft
1. Install:
lRoller 1
lCollar 2
lTorsion spring 3
lShift shaft 4
NOTE:
Apply the engine oil on the roller and shift
shaft.
Kick axle assembly
1. Install:
lKick gear 1
lPlain washer 2
lCirclip 3
lRatchet wheel 4
lSpring 5
lPlain washer 6
lCirclip 7
To kick axle 8.
NOTE:
lApply the molybdenum disulfide oil on the
kick gear inner circumference.
lAlign the punch mark a on the ratchet wheel
with the punch mark b on the kick axle.
New
New
2. Install:
lTorsion spring 1
To kick axle 2.
NOTE:
Make sure the stopper a of the torsion spring
fits into the hole b on the kick axle.

4 - 72
ENGKICK AXLE AND SHIFT SHAFT
3. Install:
lSpring guide 1
NOTE:
Slide the spring guide into the kick axle, make
sure the groove a in the spring guide fits on
the stopper of the torsion spring.
4. Install:
lKick axle assembly 1
lPlain washer 2
NOTE:
lApply the engine oil on the kick axle.
lSlide the kick axle assembly into the crank-
case, make sure the kick axle stopper a fit
into their home position 3.
5. Hook:
lTorsion spring 1
NOTE:
Turn the torsion spring clockwise and hook
into the proper hole a in the crankcase.
Kick idle gear
1. Install:
lKick idle gear 1
lPlain washer 2
lCirclip 3
NOTE:
lInstall the kick idle gear with its depressed
side a toward you.
lApply the engine oil on the kick idle gear
inner circumference.
New

4 - 77
ENGENGINE REMOVAL
EC4M0000
ENGINE REMOVAL
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the frame.
WARNING
Support the machine securely so there is no
danger of it falling over.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Carburetor Refer to “CARBURETOR” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Clutch cable Disconnect at engine side.
Decompression cable and guide Disconnect at engine side.
Radiator Refer to “RADIATOR” section.
Shift pedal Refer to “CDI MAGNETO” section.
Cylinder head breather hose and
oil tank breather hoseRefer to “CAMSHAFTS” section.
Drain the engine oil Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Spark plug cap
Disconnect the CDI magneto lead.