light YAMAHA WR 426F 2001 Owner's Manual

3 - 44
INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
2. Inspect:
lBearing free play
Exist play ® Replace.
STEERING HEAD INSPECTION AND
ADJUSTMENT
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Check:
lSteering shaft
Grasp the bottom of the forks and gen-
tly rock the fork assembly back and
forth.
Free play ® Adjust steering head.
3. Check:
lSteering smooth action
Turn the handlebar lock to lock.
Unsmooth action ® Adjust steering ring
nut.
4. Adjust:
lSteering ring nut
Steering ring nut adjustment steps:
lRemove the headlight.
lRemove the handlebar and handle crown.
lLoosen the ring nut 1 using the ring nut
wrench 2.
Ring nut wrench:
YU-33975/90890-01403

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INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
lTighten the ring nut 3 using ring nut
wrench 4.
NOTE:
Set the torque wrench to the ring nut wrench
so that they form a right angle.
Ring nut wrench:
YU-33975/90890-01403
T R..
Ring nut (initial tightening):
38 Nm (3.8 m • kg, 27 ft • lb)
lLoosen the ring nut one turn.
lRetighten the ring nut using the ring nut
wrench.
WARNING
Avoid over-tightening.
T R..
Ring nut (final tightening):
7 Nm (0.7 m • kg, 5.1 ft • lb)
lCheck the steering shaft by turning it lock
to lock. If there is any binding, remove the
steering shaft assembly and inspect the
steering bearings.
lInstall the handle crown 5, steering shaft
nut 6, handlebar 7, handlebar holder 8
and headlight 9.
NOTE:
lThe upper handlebar holder should be
installed with the punched mark a for-
ward.
lInsert the end of fuel breather hose 0 into
the hole of the steering shaft.
CAUTION:
First tighten the bolts on the front side of
the handlebar holder, and then tighten
the bolts on the rear side.
T R..
Steering shaft nut:
145 Nm (14.5 m • kg, 105 ft • lb)
Handlebar upper holder:
28 Nm (2.8 m • kg, 20 ft • lb)
Pinch bolt (handle crown):
23 Nm (2.3 m • kg, 17 ft • lb)
Headlight:
7 Nm (0.7 m • kg, 5.1 ft • lb)

3 - 46
INSP
ADJ
LUBRICATION
LUBRICATION
To ensure smooth operation of all compo-
nents, lubricate your machine during setup,
after break-in, and after every race.
1All control cable
2Clutch lever pivot
3Shift pedal pivot
4Footrest pivot
5Throttle-to-handlebar contact
6Drive chain
7Tube guide cable winding portion
8Throttle cable end
9Clutch cable end
0Decompression cable endUse Yamaha cable lube or equivalent on these
areas.
õUse SAE10W-30 motor oil or suitable chain
lubricants.
‚Lubricate the following areas with high quality,
lightweight lithium-soap base grease.
CAUTION:
Wipe off any excess grease, and avoid get-
ting grease on the brake discs.
AAA
AAB
CC

3 - 47
INSP
ADJ
ELECTRICAL/SPARK PLUG INSPECTION
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
lSpark plug
2. Inspect:
lElectrode 1
Wear/damage ® Replace.
lInsulator color 2
Normal condition is a medium to light
tan color.
Distinctly different color ® Check the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure:
lPlug gap a
Use a wire gauge or thickness gauge.
Out of specification ® Re-gap.
Spark plug gap:
0.7 ~ 0.8 mm (0.028 ~ 0.031 in)
4. Clean the plug with a spark plug cleaner
if necessary.
5. Tighten:
lSpark plug
NOTE:
lBefore installing a spark plug, clean the gas-
ket surface and plug surface.
lFinger-tighten a the spark plug before
torquing to specification b.
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)

3 - 48
INSP
ADJ
IGNITION TIMING CHECK
IGNITION TIMING CHECK
1. Remove:
lTiming plug 1
2. Attach:
lTiming light
lInductive tachometer
To the spark plug lead.
3. Check:
lIgnition timing
Timing light:
YM-33277-A/90890-03141
Inductive tachometer:
YU-08036-B
Engine tachometer:
90890-03113
Checking steps:
lStart the engine and let it warm up. Let the
engine run at the specified speed.
Engine speed:
1,700 ~ 1,900 r/min
lVisually check the stationary pointer a is
within the firing range b on the rotor.
Incorrect firing range ® Check rotor and
pickup assembly.
4. Install:
lTiming plug

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INSP
ADJ
REPLACING THE HEADLIGHT BULBS
REPLACING THE HEADLIGHT BULBS
1. Remove:
lHeadlight
Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section in the CHAP-
TER 4.
2. Remove:
lHeadlight bulb holder cover 1
3. Detach:
lHeadlight bulb holder 1
4. Remove:
lHeadlight bulb 2
WARNING
Since the headlight bulb gets extremely
hot, keep flammable products and your
hands away from the bulb unit it has
cooled down.
5. Install:
lHeadlight bulb
Secure the new headlight bulb with the
headlight bulb holder.
CAUTION:
Avoid touching the glass part of the head-
light bulb to keep it free form oil, otherwise
the transparency of the glass, the life of the
bulb and the luminous flux will be
adversely affected. If the headlight bulb
gets soiled, thoroughly clean it with a cloth
moistened with alcohol or lacquer thinner.
6. Attach:
lHeadlight bulb holder
7. Install:
lHeadlight bulb holder cover
8. Install:
lHeadlight
Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section in the CHAP-
TER 4.
New
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)

3 - 50
INSP
ADJ
ADJUSTING THE HEADLIGHT BEAMS
ADJUSTING THE HEADLIGHT BEAMS
1. Adjust:
lHeadlight beam (vertically)
Adjusting steps:
lTurn the adjusting screw 1 in direction a
or b.
Direction a Headlight beam is raised.
Direction b Headlight beam is lowered.

ENG

4 - 1
3EC400000
ENGINE
EC4R0000
SEAT, FUEL TANK AND SIDE COVERS
Extent of removal:
1
Seat removal
2
Fuel tank removal
3
Side covers removal
4
Headlight removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removal
SEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Turn the fuel cock to “OFF”.
Disconnect the fuel hose.
1 Seat 1
2 Air scoop (left and right) 2
3 Fitting band 1 Remove on fuel tank side.
4 Bolt (fuel tank) 2
5 Fuel tank 1
6 Side cover (left) 1
7 Side cover (right) 1
8 Headlight coupler 1
9 Headlight 1
13
4
2
3

SEAT, FUEL TANK AND SIDE COVERS



4

4 - 17
ENGCARBURETOR
10. Install:
lStarter jet 1
lPilot jet 2
lSpacer 3
lNeedle jet 4
lMain jet 5
11. Install:
lValve seat
lScrew (valve seat) 1
lNeedle valve 2
lFloat 3
lFloat pin 4
NOTE:
lAfter installing the needle valve to the float,
install them to the carburetor.
lCheck the float for smooth movement.
12. Install:
lPilot screw 1
lSpring 2
lWasher 3
lO-ring 4
* Except for USANote the following installation points:
lTurn in the pilot screw until it is lightly
seated.
lTurn out the pilot screw by the number of
turns recorded before removing.
Pilot screw:
WR426F: 1-5/8 turns out
*7/8 turns out
WR400F: 1-1/2 turns out
(example)
13. Install:
lO-ring
lFloat chamber 1
lScrew (float chamber) 2
lCable holder (throttle stop screw cable)
3
lHose holder (carburetor breather hose)
4
WR426F
õWR400F421 3
44õ

4 - 26
ENGCAMSHAFTS
Timing chain tensioner
1. Check:
lWhile pressing the tensioner rod lightly
with fingers, use a thin screwdriver 1
and wind the tensioner rod up fully
clockwise.
lWhen releasing the screwdriver by
pressing lightly with fingers, make sure
that the tensioner rod will come out
smoothly.
lIf not, replace the tensioner assembly.
ASSEMBLY AND INSTALLATION
1. Install:
lExhaust camshaft 1
lIntake camshaft 2
Installation steps:
lTurn the crankshaft counterclockwise until
the “I” mark a on the rotor is aligned with
the stationary pointer b on the crankcase
cover.
lFit the timing chain 3 onto both camshaft
sprockets and install the camshafts on the
cylinder head.
NOTE:
The camshafts should be installed onto the
cylinder head so that the exhaust cam
sprocket punch mark c and the intake cam
sprocket punch mark d align with the sur-
face of the cylinder head.
CAUTION:
Do not turn the crankshaft during the
camshaft installation. Damage or
improper valve timing will result.