clock YAMAHA YZ426F 2000 Owners Manual

SPEC

2 - 6
MAINTENANCE SPECIFICATIONS
Stem runout limit ---- 0.01 mm
(0.0004 in)
Valve seat width IN0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)----
EX 0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)----
Valve spring:
Free length IN 39.42 mm (1.55 in) 37.5 mm
(1.48 in)
EX 41.80 mm (1.65 in) 39.8 mm
(1.57 in)
Set length (valve closed) IN 32.87 mm (1.29 in) ----
EX 35.35 mm (1.39 in) ----
Compressed pressure
(installed) IN 124 ~ 136 N
(12.6 ~ 13.8 kg, 27.78 ~ 30.42 lb)----
EX 123 ~ 143 N
(12.6 ~ 14.6 kg, 27.78 ~ 32.19 lb)----
Tilt limit IN ----2.5˚/ 1.7 mm
(2.5˚/0.067 in)
EX ----2.5˚/1.8 mm
(2.5˚/0.071 in)
Direction of winding
(top view) IN Clockwise ----
EX Clockwise ----
Piston:
Piston to cylinder clearance 0.040 ~ 0.065 mm
(0.0016 ~ 0.0026 in)0.1 mm
(0.004 in)
Piston size “D” 94.945 ~ 94.960 mm
(3.738 ~ 3.739 in)----
Measuring point “H” 9 mm (0.354 in) ----
Piston off-set 1 mm (0.0394 in) ----Item Standard Limit
*
H
D

3 - 5
INSP
ADJ

EC350000
ENGINE
EC351011
COOLANT LEVEL INSPECTION
WARNING

Do not remove the radiator cap
1
, drain
bolt and hoses when the engine and radia-
tor are hot. Scalding hot fluid and steam
may be blown out under pressure, which
could cause serious injury.
When the engine has cooled, place a thick
towel over the radiator cap, slowly rotate
the cap counterclockwise to the detent.
This procedure allows any residual pres-
sure to escape. When the hissing sound
has stopped, press down on the cap while
turning counterclockwise and remove it.
CAUTION:

Hard water or salt water is harmful to the
engine parts. You may use distilled water, if
you can’t get soft water.
1. Place the machine on a level place, and
hold it in an upright position.
2. Remove:
l
Radiator cap
3. Check:
l
Coolant level
a

Coolant level low
®
Add coolant.
1
Radiator
ENGINE/COOLANT LEVEL INSPECTION

3 - 11
INSP
ADJTHROTTLE LUBRICATION/
DECOMPRESSION LEVER ADJUSTMENT
EC35S002
THROTTLE LUBRICATION
1. Remove:
lRubber cover 1
lThrottle cable cap 2
2. Apply:
lLithium soap base grease
On the throttle cable end a.
3. Install:
lThrottle cable cap
DECOMPRESSION LEVER ADJUSTMENT
1. Check:
lDecompression lever free play
2. Adjust:
lDecompression lever free play Checking steps:
lRemove the timing plug.
lTurn the crankshaft counterclockwise to
align the T.D.C. mark a on the rotor with
the align mark b on the crankcase cover
when piston is at T.D.C. on compression
stroke.
lCheck the free play c.
Free play:
5 ~ 9 mm (0.20 ~ 0.35 in)
Adjustment steps:
lLoosen the locknut 1.
lTurn the adjuster 2 in or out until the
adjustment is suitable.
lTighten the locknut.
CAUTION:
After the adjustment, start the engine
and make sure that the engine does not
stop when the handlebars are turned
fully both ways. If the decompression
cable is too tense, the engine will stop
by the decompression system.

3 - 19
INSP
ADJ
VALVE CLEARANCE ADJUSTMENT
4. Remove:
lTiming plug 1
lStraight plug 2
lO-ring
5. Check:
lValve clearance
Out of specification ® Adjust.
Valve clearance (cold):
Intake valve:
0.15 ~ 0.20 mm (0.0059 ~ 0.0079 in)
Exhaust valve:
0.25 ~ 0.30 mm (0.0098 ~ 0.0118 in)
Checking steps:
lTurn the crankshaft counterclockwise with
a wrench.
lAlign the T.D.C. mark a on the rotor with
the align mark b on the crankcase cover
when piston is at T.D.C. on compression
stroke.
lMeasure the valve clearance using a
feeler gauge 1.
NOTE:
Squeezing the decompressor lever allows
the crankshaft to be turned easily.
NOTE:
TDC on compression stroke can be found
when the cam lobes are opposite each
other as shown.
NOTE:
Record the measured reading if the clear-
ance is incorrect.

3 - 22
INSP
ADJ
VALVE CLEARANCE ADJUSTMENT
7. Install:
lAll removed parts
NOTE:
Install all removed parts in reversed order of
their removal. Note the following points.
lInstall the timing chain tensioner.
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
NOTE:
lRefer to “CAMSHAFTS” section in the
CHAPTER 4.
lTurn the crankshaft counterclockwise sev-
eral turns so that the installed parts settle
into the right position.
lRecheck the valve clearance.
lIf the clearance is still incorrect, repeat all
the clearance adjustment steps until the
specified clearance is obtained.

3 - 33
INSP
ADJ
FRONT FORK INSPECTION
3. Adjust:
lDrive chain slack
Drive chain slack adjustment steps:
lLoosen the axle nut 1 and locknuts 2.
lAdjust chain slack by turning the adjusters
3.
To tighten ® Turn adjuster 3 counter-
clockwise.
To loosen ® Turn adjuster 3 clockwise
and push wheel forward.
lTurn each adjuster exactly the same
amount to maintain correct axle alignment.
(There are marks a on each side of chain
puller alignment.)
lTighten the axle nut while pushing down
the drive chain.
T R..
Axle nut:
125 Nm (12.5 m • kg, 90 ft • lb)
lTighten the locknuts.
NOTE:
Turn the adjuster so that the chain is in line
with the sprocket, as viewed from the rear.
CAUTION:
Too small chain slack will overload the
engine and other vital parts; keep the
slack within the specified limits.
EC36C000
FRONT FORK INSPECTION
1. Inspect:
lFront fork smooth action
Operate the front brake and stroke the
front fork.
Unsmooth action/oil leakage ® Repair
or replace.

4 - 5
ENG

RADIATOR
EC456000
HANDLING NOTE
WARNING

Do not remove the radiator cap when the
engine and radiator are hot. Scalding hot
fluid and steam may be blown out under
pressure, which could cause serious
injury.
When the engine has cooled, open the radi-
ator cap by the following procedure:
Place a thick rag, like a towel, over the radi-
ator cap, slowly rotate the cap counter-
clockwise to the detent. This procedure
allows any residual pressure to escape.
When the hissing sound has stopped,
press down on the cap while turning coun-
terclockwise and remove it.
EC454000
INSPECTION
EC444100
Radiator
1. Inspect:
l
Radiator core
1

Obstruction
®
Blow out with com-
pressed air through rear of the radiator.
Bent fin
®
Repair/replace.
EC455000
ASSEMBLY AND INSTALLATION
EC445350
Radiator
1. Install:
l
Pipe 1
1

l
Hose 1
2

l
Pipe 2
3

l
Hose 3
4

l
Hose 4
5

2. Install:
l
Hose 2
1

l
Radiator (left)
2

4 - 19
ENGCAMSHAFTS
REMOVAL POINTS
Camshaft
1. Remove:
lTiming plug 1
lStraight plug 2
2. Align:
l“I” mark
With stationary pointer.
Checking steps:
lTurn the crankshaft counterclockwise with
a wrench.
lAlign the “I” mark a on the rotor with the
stationary pointer b on the crankcase
cover. When the “I” mark is aligned with
the stationary pointer, the piston is at the
Top Dead Center (T.D.C.).
NOTE:
lIn order to be sure that the piston is at Top
Dead Center, the punch mark c on the
exhaust camshaft and the punch mark d
on the intake camshaft must align with the
cylinder head surface, as shown in the
illustration.
lIf there is no clearance, rotate the crank-
shaft counterclockwise one turn.
3. Loosen:
lCamshaft sprocket bolts
lTensioner cap bolt 1
4. Remove:
lTiming chain tensioner 2
5. Remove:
lBolt (camshaft cap) 1
lCamshaft caps 2
NOTE:
Remove the bolts (camshaft cap) in a criss-
cross pattern, working from the inside out.
CAUTION:
The bolts (camshaft cap) must be removed
evenly to prevent damage to the cylinder
head, camshafts or camshaft caps.

4 - 22
ENG

CAMSHAFTS
Timing chain tensioner
1. Check:
l
While pressing the tensioner rod lightly
with fingers, use a thin screwdriver
1
and wind the tensioner rod up fully
clockwise.
l
When releasing the screwdriver by
pressing lightly with fingers, make sure
that the tensioner rod will come out
smoothly.
l
If not, replace the tensioner assembly.
ASSEMBLY AND INSTALLATION
1. Install:
l
Exhaust camshaft
1

l
Intake camshaft
2

Installation steps:
l
Turn the crankshaft counterclockwise until
the “I” mark
a
on the rotor is aligned with
the stationary pointer
b
on the crankcase
cover.
l
Fit 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.

4 - 23
ENG

CAMSHAFTS
2. Install:
l
Timing chain tensioner
3. Turn:
l
Crankshaft
Counterclockwise several turns
4. Check:
l
Rotor “I” mark
Align with the crankcase stationary
pointer.
l
Camshaft match marks
Align with the cylinder head surface.
Out of alignment
®
Adjust.
.
l
Install the dowel pins, clips and camshaft
caps
4
.
T R..

Bolt (camshaft cap):
10 Nm (1.0 m • kg, 7.2 ft • lb)
.
Installation steps:
l
While pressing the tensioner rod lightly with
fingers, use a thin screwdriver and wind the
tensioner rod up fully clockwise.
l
With the rod fully wound and the chain ten-
sioner UP mark
a
facing upward, install the
gasket
1
and the chain tensioner
2
, and
tighten the bolt
3
to the specified torque.
T R..

Bolt (timing chain tensioner):
10 Nm (1.0 m • kg, 7.2 ft • lb)
l
Release the screwdriver, check the ten-
sioner rod to come out and tighten the
gasket
4
and the cap bolt
5
to the speci-
fied torque.
T R..

Tensioner cap bolt:
7 Nm (0.7 m • kg, 5.1 ft • lb)
CAUTION:
Do not turn the crankshaft during the
camshaft installation. Damage or
improper valve timing will result.
NOTE:
Tighten the bolts (camshaft cap) 5 in a
crisscross pattern.
CAUTION:
The bolts (camshaft cap) must be tightened
evenly or damage to the cylinder head,
camshaft caps and camshaft will result.