wheel 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 - 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

GEN
INFO
1 - 19
TORQUE-CHECK POINTS
TORQUE-CHECK POINTS
NOTE:
Concerning the tightening torque, refer to
“MAINTENANCE SPECIFICATIONS” section
in the CHAPTER 2.
Frame to rear frame
Fuel tank to frame
Silencer to rear frame
Frame to engine
Engine bracket to engine
Engine bracket to frame
Steering shaft to frame
Steering shaft to handle crown
Handle crown to handlebar
Front fork to handle crown
Front fork to under bracket
Assembly of links
Link to frame
Link to shock absorber
Link to swingarm
Shock absorber to frame
Tightening of pivot shaft
Tightening of front axle
Tightening of axle holder
Tightening of rear axle
Wheel to sprocket
Caliper to front fork
Brake disc to wheel
Tightening of union bolt
Master cylinder to handleber
Tightening of air bleeder
Brake pedal to frame
Brake disc to wheel
Tightening of union bolt
Master cylinder to frame
Tightening of air bleeder
Fuel tank to fuel cock Frame construction
Combined seat and tank
Exhaust system
Engine mounting
Steering Steering shaft to
handlebar
Suspension Front Steering shaft to front
fork
Rear For link type
Rear Installation of shock
absorber
Rear Installation of swing-
arm
Wheel Installation of wheel Front
Rear
Brake Front
Rear
Fuel system

1 - 20
GEN
INFO
CLEANING AND STORAGE
EC1B0000
CLEANING AND STORAGE
EC1B1000
CLEANING
Frequent cleaning of your machine will
enhance its appearance, maintain good over-
all performance, and extend the life of many
components.
1. Before washing the machine, block off
the end of the exhaust pipe to prevent
water from entering. A plastic bag
secured with a rubber band may be used
for this purpose.
2. If the engine is excessively greasy, apply
some degreaser to it with a paint brush.
Do not apply degreaser to the chain,
sprockets, or wheel axles.
3. Rinse the dirt and degreaser off with a
garden hose; use only enough pressure
to do the job.
CAUTION:
Excessive hose pressure may cause water
seepage and contamination of wheel bear-
ings, front forks, brakes and transmission
seals. Many expensive repair bills have
resulted from improper high pressure
detergent applications such as those avail-
able in coin-operated car washers.
4. After the majority of the dirt has been
hosed off, wash all surfaces with warm
water and a mild detergent. Use an old
toothbrush to clean hard-to-reach places.
5. Rinse the machine off immediately with
clean water, and dry all surfaces with a
soft towel or cloth.
6. Immediately after washing, remove
excess water from the chain with a paper
towel and lubricate the chain to prevent
rust.
7. Clean the seat with a vinyl upholstery
cleaner to keep the cover pliable and
glossy.

1 - 21
GEN
INFO
CLEANING AND STORAGE
8. Automotive wax may be applied to all
painted or chromed surfaces. Avoid com-
bination cleaner-waxes, as they may con-
tain abrasives.
9. After completing the above, start the
engine and allow it to idle for several min-
utes.
EC1B2001
STORAGE
If your machine is to be stored for 60 days or
more, some preventive measures must be
taken to avoid deterioration. After cleaning the
machine thoroughly, prepare it for storage as
follows:
1. Drain the fuel tank, fuel lines, and the
carburetor float bowl.
2. Remove the spark plug, pour a table-
spoon of SAE 10W-30 motor oil in the
spark plug hole, and reinstall the plug.
With the engine stop switch pushed in,
kick the engine over several times to coat
the cylinder walls with oil.
3. Remove the drive chain, clean it thor-
oughly with solvent, and lubricate it.
Reinstall the chain or store it in a plastic
bag tied to the frame.
4. Lubricate all control cables.
5. Block the frame up to raise the wheels off
the ground.
6. Tie a plastic bag over the exhaust pipe
outlet to prevent moisture from entering.
7. If the machine is to be stored in a humid
or salt-air environment, coat all exposed
metal surfaces with a film of light oil. Do
not apply oil to rubber parts or the seat
cover.
NOTE:
Make any necessary repairs before the
machine is stored.

SPEC

2 - 1
GENERAL SPECIFICATIONS
EC200000
SPECIFICATIONS
EC211000
GENERAL SPECIFICATIONS
Model name: YZ426FP (USA)
YZ426F (EUROPE)
YZ426F(P) (CDN, AUS, NZ, ZA)
Model code number: 5SF1 (USA)
5SF2 (EUROPE)
5SF4 (CDN, AUS, NZ, ZA)
Dimensions:
Overall length 2,171 mm (85.5 in)
Overall width 827 mm (32.6 in)
Overall height 1,303 mm (51.3 in)
Seat height 998 mm (39.3 in)
Wheelbase 1,490 mm (58.7 in)
Minimum ground clearance 373 mm (14.7 in)
Basic weight:
With oil and full fuel tank 113.0 kg (249 lb)
Engine:
Engine type Liquid cooled 4-stroke, DOHC
Cylinder arrangement Single cylinder, forward inclined
Displacement 426 cm
3

(15.0 Imp oz, 14.4 US oz)
Bore

×

stroke 95.0
×
60.1 mm (3.74
×
2.37 in)
Compression ratio 12.5 : 1
Starting system Kick starter
Lubrication system: Dry sump
Oil type or grade:
Engine oil (For USA and CDN)
At 5 ˚C (40 ˚F) or higher
Å

Yamalube 4 (20W-40) or SAE 20W-40 type SH
motor oil (Non-Friction modified)
At 15 ˚C (60 ˚F) or lower
ı

Yamalube 4 (10W-30) or SAE 10W-30 type SH
motor oil (Non-Friction modified) and/or
Yamalube 4-R (15W-50) (Non-Friction modi-
fied)
(Except for USA and CDN)
API “SH” or higher grade
-20
-4-10
140
3010
5020
6830
8640 50
104
122°CTemp.
°F
10W-30
10W-40
20W-40
20W-50
15W-40

2

SPEC

2 - 3
GENERAL SPECIFICATIONS
Brake:
Front brake type Single disc brake
Operation Right hand operation
Rear brake type Single disc brake
Operation Right foot operation
Suspension:
Front suspension Telescopic fork
Rear suspension Swingarm (link type monocross suspension)
Shock absorber:
Front shock absorber Coil spring/oil damper
Rear shock absorber Coil spring/gas, oil damper
Wheel travel:
Front wheel travel 300 mm (11.8 in)
Rear wheel travel 315 mm (12.4 in)
Electrical:
Ignition system CDI magneto

SPEC
2 - 12
MAINTENANCE SPECIFICATIONS
NOTE:
- marked portion shall be checked for torque tightening after break-in or before each race. Oil strainer (frame) M18 × 1.5 1 90 9.0 65
Crankcase bearing stopper M6 × 1.0 15 10 1.0 7.2
Drive axle oil seal stopper M6 × 1.0 2 10 1.0 7.2
Ratchet wheel guide M6 × 1.0 2 12 1.2 8.7
Kick crank M8 × 1.25 1 33 3.3 24
Primary drive gear M20 × 1.0 1 75 7.5 54
Clutch boss M20 × 1.0 1 75 7.5 54
Clutch spring M6 × 1.0 6 8 0.8 5.8
Balancer driven gear M14 × 1.0 1 50 5.0 36
Balancer weight plate M6 × 1.0 3 10 1.0 7.2
Drive sprocket M20 × 1.0 1 75 7.5 54
Shift guide M6 × 1.0 2 10 1.0 7.2
Stopper lever M6 × 1.0 1 10 1.0 7.2
Segment M8 × 1.25 1 30 3.0 22
Neutral switch M5 × 0.8 2 4 0.4 2.9 Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb

SPEC
2 - 14
MAINTENANCE SPECIFICATIONS
Wheel:
Front wheel type Spoke wheel ----
Rear wheel type Spoke wheel ----
Front rim size/material 21 × 1.60/Aluminum ----
Rear rim size/material 19 × 2.15/Aluminum ----
Rim runout limit:
Radial ---- 2.0 mm (0.08 in)
Lateral ---- 2.0 mm (0.08 in)
Drive chain:
Type/manufacturer DID520DMA2 SDH/DAIDO ----
Number of links 113 links + joint ----
Chain slack 40 ~ 50 mm (1.6 ~ 2.0 in) ----
Chain length (10 links) ----152.5 mm (6.00 in)
Front disc brake:
Disc outside dia. × Thickness 250 × 3.0 mm (9.84 × 0.12 in) 250 × 2.5 mm
(9.84 × 0.10 in)
Pad thickness 4.4 mm (0.17 in) 1 mm (0.04 in)
Master cylinder inside dia. 11.0 mm (0.433 in) ----
Caliper cylinder inside dia. 27.0 mm (1.063 in) × 2 ----
Brake fluid type DOT #4 ----
Rear disc brake:
Disc outside dia. × Thickness 245 × 4.0 mm (9.65 × 0.16 in) 245 × 3.5 mm
(9.65 × 0.14 in)
Deflection limit ----0.15 mm (0.006 in)
Pad thickness 6.4 mm (0.25 in) 1.0 mm (0.04 in)
Master cylinder inside dia. 12.7 mm (0.500 in) ----
Caliper cylinder inside dia. 27.0 mm (1.063 in) × 1 ----
Brake fluid type DOT #4 ----
Brake lever and brake pedal:
Brake lever position 95 mm (3.74 in) ----
Brake pedal height
(vertical height below footrest top)5 mm (0.20 in) ----
Clutch lever free play (lever end) 8 ~ 13 mm (0.31 ~ 0.51 in) ----
Throttle grip free play 3 ~ 5 mm (0.12 ~ 0.20 in) ----Item Standard Limit

SPEC
2 - 15
MAINTENANCE SPECIFICATIONS
NOTE:
1. First, tighten the ring nut approximately 38 Nm (3.8 m • kg, 27 ft • lb) by using the ring nut
wrench, then loosen the ring nut one turn.
2. Retighten the ring nut 7 Nm (0.7 m • kg, 5.1 ft • lb). Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb
Handle crown and outer tube M8 × 1.25 4 23 2.3 17
Under bracket and outer tube M8 × 1.25 4 20 2.0 14
Handle crown and steering shaft M24 × 1.0 1 145 14.5 105
Handlebar holder (upper) M8 × 1.25 4 28 2.8 20
Steering ring nut M28 × 1.0 1 Refer to NOTE.
Front fork and cap bolt M48 × 1.0 2 30 3.0 22
Front fork and base valve M30 × 1.0 2 55 5.5 40
Cap bolt and damper rod (front fork) M12 × 1.25 2 29 2.9 21
Bleed screw (front fork) and cap bolt M5 × 0.8 2 1 0.1 0.7
Front fork and protector M6 × 1.0 6 10 1.0 7.2
Front fork and brake hose holder M6 × 1.0 2 10 1.0 7.2
Front fork and hose cover M8 × 1.25 1 16 1.6 11
Front fork and hose cover M6 × 1.0 1 7 0.7 5.1
Throttle cable cap M5 × 0.8 2 4 0.4 2.9
Clutch lever holder M5 × 0.8 2 4 0.4 2.9
Clutch lever mounting M6 × 1.0 1 2 0.2 1.4
Decompression lever holder M5 × 0.8 2 4 0.4 2.9
Front brake master cylinder and bracket M6 × 1.0 2 9 0.9 6.5
Front brake master cylinder cap M4 × 0.7 2 2 0.2 1.4
Brake lever mounting (bolt) M6 × 1.0 1 6 0.6 4.3
Brake lever mounting (nut) M6 × 1.0 1 6 0.6 4.3
Brake lever position locknut M6 × 1.0 1 5 0.5 3.6
Cable guide (front brake hose) and guide stay M5 × 0.8 1 4 0.4 2.9
Front brake hose union bolt (master cylinder) M10 × 1.25 1 30 3.0 22
Front brake hose union bolt (caliper) M10 × 1.25 1 30 3.0 22
Front brake caliper and front fork M8 × 1.25 2 23 2.3 17
Brake caliper (front and rear) and pad pin plug M10 × 1.0 1 3 0.3 2.2
Brake caliper (front and rear) and pad pin M10 × 1.0 1 18 1.8 13
Brake caliper (front and rear) and bleed screw M8 × 1.25 1 6 0.6 4.3
Front wheel axle and nut M16 × 1.5 1 105 10.5 75
Front wheel axle holder M8 × 1.25 4 23 2.3 17
Front brake disc and wheel hub M6 × 1.0 6 12 1.2 8.7
Rear brake disc and wheel hub M6 × 1.0 6 14 1.4 10
Brake pedal mounting M8 × 1.25 1 26 2.6 19
Rear brake master cylinder and frame M6 × 1.0 2 10 1.0 7.2