2001 YAMAHA YZ426F engine

SPEC
2 - 18
EC220001
GENERAL TORQUE SPECIFICATIONS
This chart specifies torque for standard fasten-
ers with standard I.S.O. pitch threads. Torque
specifications for special components or
assemblies are included in the applicable sec-
tions of this book. To avoid warpage, tighten
multi-fastener assemblies in a crisscross fash-
ion, in progressive stages, until full torque is
reached. Unless otherwise specified, torque
specifications call for clean, dry threads. Com-
ponents should be at room temperature.
A: Distance between flats
B: Outside thread diameter
EC230000
DEFINITION OF UNITS
A
(Nut)B
(Bolt)TORQUE
SPECIFICATION
Nm m•kg ft•lb
10 mm
12 mm
14 mm
17 mm
19 mm
22 mm6 mm
8 mm
10 mm
12 mm
14 mm
16 mm6
15
30
55
85
1300.6
1.5
3.0
5.5
8.5
134.3
11
22
40
61
94
Unit Read Definition Measure
mm
cmmillimeter
centimeter10
-3 meter
10-2 meterLength
Length
kg kilogram 10
3 gram Weight
N Newton 1 kg ´ m/sec
2 Force
Nm
m • kgNewton meter
Meter kilogramN ´ m
m ´ kgTorque
Torque
Pa Pascal N/m
2Pressure
N/mm Newton per millimeter N/mm Spring rate
L
cm
3 Liter
Cubic centimeter—
—Volume or capacity
Volume or capacity
r/min Revolution per minute — Engine speed
GENERAL TORQUE SPECIFICATIONS/
DEFINITION OF UNITS

2 - 21
SPEC

CABLE ROUTING DIAGRAM
EC240000
CABLE ROUTING DIAGRAM
1
Hose guide
2
Brake hose
3
Fuel tank breather hose
4
Oil tank breather hose
5
Clamp
6
“ENGINE STOP” button lead
7
Sub wire harness
8
TPS (throttle position
sensor) lead
9
Neutral switch lead
0
Oil hose
A
Hose holder
B
CDI magneto lead
C
Clutch cable
D
Cylinder head breather hose
E
Carburetor breather hose
F
Overflow hose

Pass the clutch cable through
the cable guide.
õ
Pass the fuel tank breather hose
between the handlebar and ten-
sion bar, then insert its end into
the hole of the number plate.
‚
Pass the decompression cable
and “ENGINE STOP” button
lead under the frame.
ë
Fasten the CDI magneto lead,
neutral switch lead and
“ENGINE STOP” button lead to
the frame with a plastic locking
tie and cut off the tie end.
ä
Pass the “ENGINE STOP” but-
ton lead along the inner side of
the oil tank breather hose.
ì
Fasten the sub wire harness
and “ENGINE STOP” button
lead to the frame in front of the
protector of the sub wire har-
ness with a plastic locking tie
and cut off the tie end.
í
Pass the cylinder head breather
hose along the right side of the
oil tank breather hose.
î
Pass the sub wire harness
between the engine brackets.
é
Fasten the sub wire harness
and “ENGINE STOP” button
lead to the frame at the rear of
the protector of the sub wire har-
ness with a plastic locking tie
and cut off the tie end.

SPEC

2 - 21
CHEMINEMENT DES CABLES
KABELFÜHRUNG
KABELFÜHRUNG
1
Kabelführung
2
Bremsschlauch
3
Kraftstofftank-Belüftungsschlauch
4
Öltank-Belüftungsschlauch
5
Kabelbinder
6
Motorstoppschalter-Kabel
7
Nebenkabelsatz
8
Drosselklappen-Positionssensor (TPS)
9
Leerlaufschalter-Kabel
0
Ölschlauch
A
Schlauchhalterung
B
CDI-Schwungradmagnetzünder-Kabel
C
Kupplungszug
D
Zylinderkopf-Entlüftungsschlauch
E
Vergaser-Entlüftungsschlauch
FAuslaufschutzschlauch
Den Kupplungszug durch die Kabelführung füh-
ren.
õDen Kraftstofftank-Belüftungsschlauch zwischen
Lenker und Zugstrebe führen und das Ende
durch die Bohrung im Nummerschild führen.
‚Den Dekompressionszug und das Motorstopp-
schalterkabel unter dem Rahmen hindurchfüh-
ren.
ëDas CDI-Schwungrad-Magnetzünderkabel, Leer-
laufschalterkabel und Motorstoppschalterkabel
mit einem Einweg-Kabelbinder am Rahmen be-
festigen und das überstehende Ende des Kabel-
binders abschneiden.
äDas Motorstoppschalter-Kabel hinter dem Öl-
tank-Belüftungsschlauch führen.
ìDen Nebenkabelsatz und das Zuleitungskabel
für den Motorstopp-Schalter vor dem Schutz des
Nebenkabelsatzes mit einem Einweg-Kabelbin-
der am Rahmen befestigen und das Ende des
Kabelbinders abschneiden.
íDen Zylinderkopf-Entlüftungsschlauch rechts
vom Öltank-Belüftungsschlauch führen.
îDen Nebenkabelsatz zwischen den Motorlagern
hindurchführen.
éDen Nebenkabelsatz und das Zuleitungskabel
für den Motorstopp-Schalter hinter dem Schutz
des Nebenkabelsatzes befestigen.
CHEMINEMENT DES CABLES
1Guide de flexible
2Tuyau de frein
3Reniflard de réservoir d’essence
4Reniflard de réservoir d’huile
5Bride
6Fil de bouton d’arrêt du moteur “ENGINE STOP”
7Faisceau de fils secondaires
8Fil de TPS (copteur du papillon d’accélération)
9Fil de contacteur de point mort
0Flexible d’huile
ASupport de flexible
BFil de magnéto CDI
CCâble d’embrayage
DReniflard de culasse
EReniflard de carburateur
FFlexible de trop-plein
Faire passer le câble d’embrayage dans le guide de
câble.
õFaire passer le reniflard du réservoir d’essence entre
le guidon et la barre de tension, puis insérer son
extrémité dans l’orifice prévu sur la plaque de
numéro.
‚Faire passer le câble de décompression et le fil de
bouton d’arrêt du moteur “ENGINE STOP” sous le
cadre.
ëAttacher le fil de magnéto CDI, le fil de contacteur de
point mort et le fil de bouton d’arrêt du moteur
“ENGINE STOP” au cadre à l’aide d’une attache en
plastique et couper l’extrémité de l’attache.
äFaire passer le fil de bouton d’arrêt du moteur
“ENGINE STOP” derrière le reniflard du réservoir
d’huile et couper l’extrémité de l’attache.
ìAttacher le faisceau de fils secondaire et le fil du bou-
ton d’arrêt du moteur “ENGINE STOP” au cadre, à
l’avant de la protection du faisceau de fils secondaire,
à l’aide d’un lien en plastique, puis couper l’extré-
mité du lien.
íFaire passer le reniflard de culasse le long du côté
droit du reniflard du réservoir d’huile.
îFaire passer le faisceau de fils secondaire par les sup-
ports du moteur.
éAttacher le faisceau de fils secondaire et le fil du bou-
ton d’arrêt du moteur “ENGINE STOP” au cadre, à
l’arrière de la protection du faisceau de fils secon-
daire.

2 - 22
SPEC

CABLE ROUTING DIAGRAM
ï
Fasten the TPS lead (in the
sub wire harness) under the
frame so that it does not con-
tact the carburetor.
ð
Fasten the TPS lead under the
coupler to the frame with a
plastic locking tie.
ñ
Pass the carburetor breather
hose and overflow hose
between the connecting rod
and cross tube (frame).
÷
Fasten the neutral switch lead
and oil hose together with a
plastic locking tie and cut off
the tie end.
ö
Fasten the cylinder head
breather hose and neutral
switch lead to the frame with a
plastic locking tie.
¯
Fasten the neutral switch lead
to the frame with a plastic
band.
¸
Fasten the cylinder head
breather hose with the hose
holder.
Î
Pass the clutch cable through
the cable guide.
å
Fasten the neutral switch lead
and CDI magneto lead together
with a plastic band.
ê
Pass the clutch cable on the
inside the cylinder head
breather hose.
æ
Pass the cylinder head
breather hose along the inner
side of the radiator pipe.
è
Pass the radiator breather
hose from the right side of the
frame to the left side, over radi-
ator pipe 1, along the inner side
of radiator hose 4 and the radi-
ator, and between the lower
engine bracket, crankcase, oil
hose and the frame.
×Pass the clutch cable between
the frame and radiator and
over the lower boss on the radi-
ator.

2 - 25
SPECCABLE ROUTING DIAGRAM
1Throttle cable
2Clamp
3Decompression cable
4Clutch cable
5Brake hose
6Hose guide
7“ENGINE STOP” button leadFasten the “ENGINE STOP” button lead to the handlebar with the
plastic band.
õPass the brake hose in front of the number plate.

SPEC
2 - 25
CHEMINEMENT DES CABLES
KABELFÜHRUNG
1Gaszug
2Kabelbinder
3Dekompressionszug
4Kupplungszug
5Bremsschlauch
6Kabelführung
7Motorstoppschalter-Kabel
Das Motorstoppschalter-Kabel mit mehrf. ver-
wendb. Kabelbinder am Lenker befestigen.
õDen Bremsschlauch vor dem Nummernschild
führen. 1Câble d’accélération
2Bride
3Câble du décompresseur
4Câble d’embrayage
5Tuyau de frein
6Guide de flexible
7Fil de bouton d’arrêt du moteur “ENGINE STOP”
Fixer le fil de bouton d’arrêt du moteur “ENGINE
STOP” au guidon à l’aide d’une attache en plastique.
õFaire passer le tuyau de frein par-devant la plaque de
numéro.

3 - 1
INSP
ADJ

MAINTENANCE INTERVALS
EC300000
REGULAR INSPECTION AND ADJUSTMENTS
MAINTENANCE INTERVALS
The following schedule is intended as a general guide to maintenance and lubrication. Bear in mind
that such factors as weather, terrain, geographical location, and individual usage will alter the
required maintenance and lubrication intervals. If you are a doubt as to what intervals to follow in
maintaining and lubricating your machine, consult your Yamaha dealer.
ItemAfter
break-inEvery
race
Every
third
(or
500 km)Every
fifth
(or
1,000 km)
As re-
quiredRemarks
ENGINE OIL
Replace
c

c

OIL FILTER
Clean
cc

VALVES
Check the valve clearances.
Inspect
Replace
c

c

c

c
The engine must be cold.
Check the valve seats
and valve stems for wear.
VALVE SPRINGS
Inspect
Replace
c

c
Check the free length and
the tilt.
VALVE LIFTERS
Inspect
Replace
c

c
Check for scratches and
wear.
CAMSHAFTS
Inspect
Replace
c

c
Inspect the camshaft sur-
face.
CAMSHAFT SPROCKETS
Inspect
Replace
c

c
Check for wear on the
teeth and for damage.
PISTON
Inspect
Clean
Replace
c

c

c

c
Inspect crack
Remove carbon
PISTON RING
Inspect
Replace
c

c

c
Check ring end gap
PISTON PIN
Inspect
Replace
c

c

CYLINDER HEAD
Inspect and clean
c
Remove carbon
Change gasket
CYLINDER
Inspect and clean
Replace
c

c
Inspect score marks
Inspect wear
CLUTCH
Inspect and adjust
Replace
c

c

c
Inspect housing, friction
plate, clutch plate and
spring
TRANSMISSION
Inspect
Replace bearing
c

c



3

3 - 4
INSP
ADJ
PRE-OPERATION INSPECTION AND MAINTENANCE
EC320000
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator filler cap.
Check the cooling system for leakage.P.3-5 ~ 9
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the
fuel line for leakage.P.1-13 ~ 14
Engine oilCheck that the oil level is correct. Check the crankcase and
frame oil line for leakage.P.3-13 ~ 17
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-9
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-10 ~ 11
Brakes Check the play of front brake and effect of front and rear brake. P.3-24 ~ 30
ChainCheck chain slack and alignment. Check that the chain is lubri-
cated properly.P.3-31 ~ 33
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-41 ~ 42
SteeringCheck that the handlebar can be turned smoothly and have no
excessive play.P.3-42 ~ 43
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage. P.3-33 ~ 40
Cables (wires)Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or
when the front forks travel up and down.—
Muffler Check that the muffler is tightly mounted and has no cracks. —
Sprocket Check that the driven sprocket tightening bolt is not loose. P.3-31
Lubrication Check for smooth operation. Lubricate if necessary. P.3-44
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-18
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-6
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs
before racing? Are inspection and maintenance completely
done?P.7-1 ~ 21