radiator YAMAHA YZ426F 2002 Owners Manual

CHAPTER 4
ENGINE
SEAT, FUEL TANK
AND SIDE COVERS
................................. 4-1
EXHAUST PIPE AND SILENCER
............ 4-2
RADIATOR
................................................ 4-4
CARBURETOR
......................................... 4-7
CAMSHAFTS
.......................................... 4-20
CYLINDER HEAD
................................... 4-27
VALVES AND VALVE SPRINGS
........... 4-31
CYLINDER AND PISTON
....................... 4-40
CLUTCH
.................................................. 4-46
OIL FILTER, WATER PUMP
AND CRANKCASE COVER (RIGHT)
.... 4-53
BALANCER
............................................ 4-60
OIL PUMP
............................................... 4-63
KICK AXLE AND SHIFT SHAFT
............ 4-67
CDI MAGNETO
....................................... 4-74
ENGINE REMOVAL
................................ 4-78
CRANKCASE AND CRANKSHAFT
....... 4-83
TRANSMISSION, SHIFT CAM
AND SHIFT FORK
.................................. 4-92
CHAPTER 5
CHASSIS
FRONT WHEEL AND REAR WHEEL
...... 5-1
FRONT BRAKE AND REAR BRAKE
..... 5-10
FRONT FORK
......................................... 5-27
HANDLEBAR
.......................................... 5-40
STEERING
.............................................. 5-46
SWINGARM
............................................ 5-51
REAR SHOCK ABSORBER
................... 5-58

GEN
INFO

1 - 1
DESCRIPTION
EC100000
GENERAL INFORMATION
EC110000
DESCRIPTION
1
Clutch lever
2
Decompression lever
3
Front brake lever
4
Throttle grip
5
Radiator cap
6
Fuel tank cap
7
Oil filler plug/dipstick
8
“ENGINE STOP” button
9
Kick starter
0
Fuel tank
A
Radiator
B
Coolant drain bolt
C
Rear brake pedal
D
Valve joint
E
Fuel cock
F
Cold starter knob
G
Hot starter knob (red)
H
Drive chain
I
Air cleaner
J
Shift pedal
K
Front fork
NOTE:


The machine you have purchased may differ
slightly from those shown in the following.

Designs and specifications are subject to
change without notice.

GEN
INFO
1 - 7
SPECIAL TOOLS
EC140001
SPECIAL TOOLS
The proper special tools are necessary for complete and accurate tune-up and assembly. Using the
correct special tool will help prevent damage caused by the use of improper tools or improvised
techniques. The shape and part number used for the special tool differ by country, so two types are
provided. Refer to the list provided to avoid errors when placing an order.
NOTE:
For U.S.A. and Canada, use part number starting with “YM-” , “YU-” or “ACC-”.
For others, use part number starting with “90890-”.
Part number Tool name/How to use Illustration
YU-1135-A, 90890-01135 Crankcase separating tool
These tool is used to remove the crankshaft from
either case.YU-1135-A 90890-01135
YU-1235, 90890-01235 Rotor holding tool
This tool is used when loosening or tightening the fly-
wheel magneto securing nut.YU-1235 90890-01235
YU-3097, 90890-01252
YU-1256Dial gauge and stand
Stand
These tools are used to check each part for runout or
bend.YU-3097
YU-125690890-01252
YU-90050, 90890-01274
YU-90050, 90890-01275
YU-91044, 90890-04081
YM-1277, 90890-01277Crankcase installing tool
Pot
Bolt
Spacer
Adapter
These tools are used to install the crankshaft.YU-90050
YM-1277
YU-9104490890-01274
90890-01275
90890-01277
90890-04081
YU-1304, 90890-01304 Piston pin puller
This tool is used to remove the piston pin.YU-1304 90890-01304
YU-24460-01, 90890-01325
YU-33984, 90890-01352Radiator cap tester
Adapter
These tools are used for checking the cooling sys-
tem.YU-24460-01
YU-3398490890-01325
90890-01352
YM-1189, 90890-01189 Flywheel puller
This tool is used to remove the flywheel magneto.YM-1189 90890-01189

SPEC

2 - 9
MAINTENANCE SPECIFICATIONS
Lubrication system:
Oil filter type Wire mesh type ----
Oil pump type Trochoid type ----
Tip clearance “A”0.12 mm or less
(0.0047 in or less)0.20 mm
(0.008 in)
Tip clearance “B”0.09 ~ 0.17 mm
(0.0035 ~ 0.0067 in)0.24 mm
(0.009 in)
Side clearance 0.03 ~ 0.10 mm
(0.0012 ~ 0.0039 in)0.17 mm
(0.007 in)
Bypass valve setting pressure 40 ~ 80 kPa (0.4 ~ 0.8 kg/cm
2

,
5.69 ~ 11.38 psi)----
Cooling:
Radiator core size
Width 117.8 mm (4.6 in) ----
Height 260 mm (10.2 in) ----
Thickness 32 mm (1.26 in) ----
Radiator cap opening pressure 110 kPa (1.1 kg/cm
2

, 15.6 psi) ----
Radiator capacity (total) 0.76 L (0.67 lmp qt, 0.80 US qt) ----
Water pump
Type Single-suction centrifugal pump ----Item Standard Limit

SPEC

2 - 11
MAINTENANCE SPECIFICATIONS
Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb
Spark plug M10S
×
1.0 1 13 1.3 9.4
Camshaft cap M6
×
1.0 10 10 1.0 7.2
Cylinder head (stud bolt) M6
×
1.0 2 7 0.7 5.1
M8
×
1.25 3 15 1.5 11
(bolt) M10
×
1.25 4 44 4.4 32
(nut) M6
×
1.0 2 10 1.0 7.2
M8
×
1.25 2 20 2.0 14
Cylinder head cover M6
×
1.0 2 10 1.0 7.2
Cylinder M6
×
1.0 1 10 1.0 7.2
Timing chain tensioner M6
×
1.0 2 10 1.0 7.2
Tensioner cap bolt M6
×
1.0 1 7 0.7 5.1
Timing chain guide (rear) M6
×
1.0 2 10 1.0 7.2
Decompression shaft M6
×
1.0 1 7 0.7 5.1
Decompression cable guide M6
×
1.0 1 10 1.0 7.2
Exhaust pipe (nut) M8
×
1.25 1 13 1.3 9.4
(bolt) M8
×
1.25 1 24 2.4 17
Silencer M8
×
1.25 2 35 3.5 25
Silencer clamp M8
×
1.25 1 20 2.0 14
Exhaust pipe protector M6
×
1.0 3 10 1.0 7.2
Clamp (air cleaner joint) M5
×
0.8 1 3 0.3 2.2
Clamp (carburetor joint) M4
×
0.7 1 3 0.3 2.2
Air filter joint clamp M6
×
1.0 1 3 0.3 2.2
Throttle cable cover M5
×
0.8 1 4 0.4 2.9
Air filter element M6
×
1.0 1 2 0.2 1.4
Radiator panel (upper) M6
×
1.0 2 10 1.0 7.2
Radiator M6
×
1.0 6 10 1.0 7.2
Radiator hose clamp M6
×
1.0 8 2 0.2 1.4
Impeller M8
×
1.25 1 14 1.4 10
Water pump housing cover M6
×
1.0 3 10 1.0 7.2
Coolant drain bolt M6
×
1.0 1 10 1.0 7.2
Oil pump cover M5
×
0.8 1 4 0.4 2.9
Oil pump M6
×
1.0 3 10 1.0 7.2
Engine oil drain bolt (oil filter) M6
×
1.0 1 10 1.0 7.2
Oil filter cover M6
×
1.0 2 10 1.0 7.2
Oil delivery pipe 1 M10
×
1.25 1 20 2.0 14
M8 × 1.25 2 18 1.8 13
Oil hose clamp–2 2 0.2 1.4
Clutch cover M6 × 1.0 7 10 1.0 7.2
Crankcase cover (right) M6 × 1.0 10 10 1.0 7.2
Crankcase cover (left) M6 × 1.0 8 10 1.0 7.2
Crankcase M6 × 1.0 12 12 1.2 8.7
Oil drain bolt (crankcase) M12 × 1.5 1 20 2.0 1.4
Oil drain bolt (frame) M8 × 1.25 1 23 2.3 17

SPEC
2 - 16
MAINTENANCE SPECIFICATIONS
NOTE:
- marked portion shall be checked for torque tightening after break-in or before each race.Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb
Rear brake reservoir tank and frame M6 × 1.0 1 10 1.0 7.2
Rear brake hose union bolt (caliper) M10 × 1.25 1 30 3.0 22
Rear brake hose union bolt (master cylinder) M10 × 1.25 1 30 3.0 22
Rear wheel axle and nut M20 × 1.5 1 125 12.5 90
Driven sprocket and wheel hub M8 × 1.25 6 42 4.2 30
Nipple (spoke)–72 3 0.3 2.2
Disc cover and rear brake caliper M6 × 1.0 2 7 0.7 5.1
Protector and rear brake caliper M6 × 1.0 2 7 0.7 5.1
Engine mounting:
Engine bracket and frame M8 × 1.25 7 34 3.4 24
Engine and frame (front) M10 × 1.25 1 69 6.9 50
Engine and frame (upper) M10 × 1.25 1 55 5.5 40
Engine and frame (lower) M10 × 1.25 1 69 6.9 50
Engine guard (lower) M8 × 1.25 1 23 2.3 17
Pivot shaft and nut M16 × 1.5 1 85 8.5 61
Relay arm and swingarm M14 × 1.5 1 80 8.0 58
Relay arm and connecting rod M14 × 1.5 1 80 8.0 58
Connecting rod and frame M14 × 1.5 1 80 8.0 58
Rear shock absorber and frame M10 × 1.25 1 56 5.6 40
Rear shock absorber and relay arm M10 × 1.25 1 53 5.3 38
Rear frame and frame M8 × 1.25 3 29 2.9 21
Swingarm and brake hose holder M5 × 0.8 4 1 0.1 0.7
Swingarm and patch M4 × 0.7 4 2 0.2 1.4
Drive chain tensioner mounting (upper) M8 × 1.25 1 19 1.9 13
Drive chain tensioner mounting (lower) M8 × 1.25 1 20 2.0 14
Chain support and swingarm M6 × 1.0 3 7 0.7 5.1
Seal guard and swingarm M5 × 0.8 4 6 0.6 4.3
Fuel tank mounting M6 × 1.0 2 10 1.0 7.2
Fuel tank and fuel cock M6 × 1.0 2 7 0.7 5.1
Fuel tank and seat set bracket M6 × 1.0 1 7 0.7 5.1
Fuel tank and hooking screw (fitting band) M6 × 1.0 1 7 0.7 5.1
Fuel tank and fuel tank bracket M6 × 1.0 4 7 0.7 5.1
Seat mounting M8 × 1.25 2 23 2.3 17
Side cover mounting M6 × 1.0 2 7 0.7 5.1
Air scoop and fuel tank M6 × 1.0 4 4 0.4 2.9
Air scoop and radiator panel (lower) M6 × 1.0 2 4 0.4 2.9
Front fender mounting M6 × 1.0 4 7 0.7 5.1
Rear fender mounting M6 × 1.0 4 7 0.7 5.1
Number plate M6 × 1.0 1 7 0.7 5.1

2 - 22
SPEC

CABLE ROUTING DIAGRAM
È
Fasten the TPS lead (in the
sub wire harness) under the
frame so that it does not con-
tact the carburetor.
Ô
Make sure that the TPS lead
coupler does not go outside the
chassis.

Fasten the TPS lead under the
coupler to the frame with a
plastic locking tie.
Ò
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.ˆFasten the cylinder head
breather hose with the hose
holder.
ØFasten the neutral switch lead
to the frame with a plastic band
ends toward the rear of the
frame.
∏Fasten the cylinder head
breather hose with the hose
holder.
ŒPass the clutch cable through
the cable guide.
ÂFasten the neutral switch lead
and CDI magneto lead together
with a plastic band.
ÍPass the clutch cable on the
inside the cylinder head
breather hose.ÊPass the cylinder head
breather hose along the inner
side of the radiator pipe.
ËPass 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 - 23
SPEC
„Pass the neutral switch lead and
CDI magneto lead through the
cable guide and over the middle
radiator mounting boss. Then, pass
the decompression cable under the
middle radiator mounting boss and
along the left side of the neutral
switch lead and CDI magneto lead.
ÙFit the brake hose into the guides
on the protector.
ÁFasten the ignition coil lead (in the
sub wire harness) on the upper
inside of the frame and cut off the
tie end.
ÛPass the ignition coil lead (in the
sub wire harness) under the cush-
ion bracket (frame).Fasten the ignition coil lead (in the
sub wire harness) to the frame
and cut off the tie end.
Pass the carburetor breather
hoses and overflow hose so that
all there hoses do not contact the
rear shock absorber.AA
AB
CABLE ROUTING DIAGRAM

2 - 24
SPECCABLE ROUTING DIAGRAM
1Clamp
2Ignition coil
3High tension cord
4CDI unit
5CDI unit band
6“ENGINE STOP” button
lead
7Throttle cable (pull)
8Throttle cable (return)
9Radiator (left)
0Radiator breather hose
ARadiator (right)
BCDI unit stay (frame)ÅFasten the ignition coil lead to the
frame with a plastic band.
ıFasten the ignition coil and ground
lead to the frame with the bolt.
ÇPass the ignition coil lead (in the
sub wire harness) so that it does
not contact the carburetor and
rear shock absorber and connect
it with the lead from the ignition
coil on the inside of the frame.
ÎPass the throttle cables over the
high tension cord.
‰Pass the throttle cables along the
outer side of the CDI unit leads.
ÏFasten the CDI unit leads and
“ENGINE STOP” button lead to the
frame at the protector of the CDI
unit leads with a plastic locking tie.
ÌPass the radiator breather hose
on the outside the CDI unit lead
and “ENGINE STOP” button lead.ÓPass the CDI unit lead and
“ENGINE STOP” button lead over
the top radiator mounting boss.
ÈPass the throttle cables and
“ENGINE STOP” button lead
through the cable guide.
ÔCross the pull and return throttle
cables before the radiator.
Pass the throttle cables, “ENGINE
STOP” button lead and CDI unit
lead through the cable guide.
ÒPass the throttle cables between
the top radiator mounting boss and
middle radiator mounting boss.
˜Pass the radiator breather hose
between the frame and the radia-
tor without pinching it.
ˆPass the radiator breather hose
behind the decompression cable.
ØInsert the CDI unit band over the
CDI unit stay (frame) as far as
possible.

3 - 2
INSP
ADJ

MAINTENANCE INTERVALS
SHIFT FORK, SHIFT CAM, GUIDE BAR
Inspect
●
Inspect wear
ROTOR NUT
Retighten
●

●

MUFFLER
Inspect and retighten
Clean
Replace
●

●

●

●
* Whichever comes first
CRANK
Inspect and clean
●

●

CARBURETOR
Inspect, adjust and clean
●

●
When using a high-pres-
sure washer, make sure
that water does not enter
the accelerator pump.
SPARK PLUG
Inspect and clean
Replace
●

●

●

DRIVE CHAIN
Lubricate, slack, alignment
Replace
●

●

●
Use chain lube
Chain slack: 40 ~ 50 mm
(1.6 ~ 2.0 in)
COOLING SYSTEM
Check coolant level and leakage
Check radiator cap operation
Replace coolant
Inspect hoses
●

●

●

●

●
Every two years
OUTSIDE NUTS AND BOLTS
Retighten
●

●
Refer to “STARTING
AND BREAK-IN” section
in the CHAPTER 1.
AIR FILTER
Clean and lubricate
Replace
●

●

●
Use foam air-filter oil
OIL STRAINER (frame)
Clean
●

FRAME
Clean and inspect
●

●

FUEL TANK, COCK
Clean and inspect
●

●

BRAKES
Adjust lever position and pedal height
Lubricate pivot point
Check brake disc surface
Check fluid level and leakage
Retighten brake disc bolts, caliper
bolts, master cylinder bolts and union
bolts
Replace pads
Replace brake fluid
●

●

●

●

●

●

●

●

●

●

●

●
Every one year
FRONT FORKS
Inspect and adjust
Replace oil
Replace oil seal
●

●

●

●

●
Suspension oil “01” ItemAfter
break-inEvery
race
Every
third
(or
500 km)Every
fifth
(or
1,000 km)
As re-
quiredRemarks
1
2
3