2002 YAMAHA YZ426F check oil

3 - 13
INSP
ADJ
ENGINE OIL LEVEL INSPECTION
6. Apply:
Lithium soap base grease
On the matching surface a on air filter
element.
7. Install:
Air filter element 1
Washer
Fitting bolt
NOTE:
Align the projection a on filter guide with the
hole b in air filter case.
T R..2 Nm (0.2 m · kg, 1.4 ft · lb)
ENGINE OIL LEVEL INSPECTION
1. Stand the motorcycle on a level surface.
NOTE:
When checking the oil level make sure that
the motorcycle is upright.
Place the motorcycle on a suitable stand.
WARNING
Never remove the oil tank cap just after
high speed operation. The heated oil could
spurt out. causing danger. Wait until the oil
cools down to approximately 70 ˚C (158 ˚F).
2. Idle the engine more than 3 minutes
while keeping the motorcycle upright.
Then stop the engine and inspect the oil
level.
3. Remove:
Oil tank cap 1

3 - 16
INSP
ADJ
ENGINE OIL REPLACEMENT
6. If the oil filter is to be replaced during this
oil change, remove the following parts
and reinstall them.
7. Install:
Plain washer 1
Oil strainer (frame) 2
Engine oil hose 3
Bolt (engine oil hose) 4
Engine oil hose clamp 5
Engine skid plate
8. Install:
Gaskets
Oil filter drain bolt
Drain bolt (crankcase)
Drain bolt (frame)
9. Fill:
Oil tank (frame)
10. Install:
Oil filler plug
11. Inspect:
Engine (for oil leaks)
Oil level
Refer to “ENGINE OIL LEVEL INSPEC-
TION”. Replacement steps:
Remove the exhaust pipe.
Remove the oil filter cover 1 and oil filter
element 2.
Check the O-rings 3, if cracked or dam-
aged, replace them with a new one.
Install the oil filter element and oil filter
cover.
T R..
Oil filter cover:
10 Nm (1.0 m • kg, 7.2 ft • lb)
Oil quantity:
Total amount:
1.5 L (1.32 Imp qt, 1.59 US qt)
Periodic oil change:
1.3 L (1.14 Imp qt, 1.37 US qt)
With oil filter replacement:
1.4 L (1.23 Imp qt, 1.48 US qt)
New
T R..90 Nm (9.0 m · kg, 65 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..2 Nm (0.2 m · kg, 1.4 ft · lb)
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..20 Nm (2.0 m · kg, 14 ft · lb)
T R..23 Nm (2.3 m · kg, 17 ft · lb)

3 - 17
INSP
ADJ
PILOT SCREW ADJUSTMENT
12. Check:
Oil pressure
Checking steps:
Slightly loosen the oil gallery bolt 1.
Start the engine and keep it idling until oil
starts to seep from the oil gallery bolt. If no
oil comes out after one minute, turn the
engine off so it will not seize.
Check oil passages, oil filter and oil pump
for damage or leakage.
Start the engine after solving the prob-
lem(s) and recheck the oil pressure.
Tighten the oil gallery bolt to specification.
T R..
Oil gallery bolt:
18 Nm (1.8 m • kg, 13 ft • lb)
PILOT SCREW ADJUSTMENT
1. Adjust:
Pilot screw 1
Adjusting steps:
NOTE:
To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot screw has
been individually set at the factory. Before
adjusting the pilot screw, turn it in fully and
count the number of turns. Record this num-
ber as the factory-set number of turns out.
Turn in the pilot screw until it is lightly
seated.
Turn out the pilot screw by the factory-set
number of turns.
Pilot screw:
1-3/8 turns out (example)

3 - 31
INSP
ADJ

SPROCKETS INSPECTION/DRIVE CHAIN INSPECTION
EC368000
SPROCKETS INSPECTION
1. Inspect:

Sprocket teeth
a

Excessive wear
→
Replace.
NOTE:

Replace the drive, driven sprockets and drive
chain as a set.
EC369002
DRIVE CHAIN INSPECTION
1. Remove:

Master link clip

Joint
1


Drive chain
2

2. Clean:

Drive chain
Place it in kerosene, and brush off as
much dirt as possible. Then remove the
chain from the kerosene and dry the
chain.
3. Measure:

Drive chain length (10 links)
a

Out of specification
→
Replace.
Drive chain length (10 links):
Limit: 152.5 mm (6.00 in)
4. Check:

Drive chain stiffness
a

Clean and oil the chain and hold as
illustrated.
Stiff
→
Replace drive chain.

3 - 32
INSP
ADJ

DRIVE CHAIN SLACK ADJUSTMENT
5. Install:

Drive chain
1


Joint
2


Master link clip
3

CAUTION:

Be sure to install the master link clip to the
direction as shown.
a
Turning direction
6. Lubricate:

Drive chain
Drive chain lubricant:
SAE 10W-30 motor oil or suit-
able chain lubricants
New

EC36A060
DRIVE CHAIN SLACK ADJUSTMENT
1. Elevate the rear wheel by placing the
suitable stand under the engine.
2. Check:

Drive chain slack
a

Above the seal guard installation bolt.
Out of specification
→
Adjust.
NOTE:

Before checking and/or adjusting, rotate the
rear wheel through several revolutions and
check the slack several times to find the tight-
est point. Check and/or adjust chain slack with
rear wheel in this “tight chain” position.
Drive chain slack:
40 ~ 50 mm (1.6 ~ 2.0 in)

4 - 65
ENGOIL PUMP
INSPECTION
Oil pump
1. Inspect:
Oil pump drive gear
Oil pump driven gear
Rotor housing
Oil pump cover
Cracks/wear/damage → Replace.
2. Measure:
Tip clearance a
Between the inner rotor 1 and the
outer rotor 2.
Tip clearance b
Between the outer rotor 2 and the rotor
housing 3.
Out of specification → Replace the oil
pump.
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 c:
0.03 ~ 0.10 mm (0.0012 ~ 0.0039 in)
: 0.17 mm (0.007 in)
3. Check:
Unsmooth → Repeat steps #1 and #2
or replace the defective parts.
ASSEMBLY AND INSTALLATION
Oil pump
1. Install:
Oil pump drive shaft 1
Washer 2
Pin 3
Inner rotor 1 4
NOTE:
Apply the engine oil on the oil pump drive
shaft and inner rotor 1.
Fit the pin into the groove in the inner rotor 1.

4 - 90
ENGCRANKCASE AND CRANKSHAFT
NOTE:
Hold the connecting rod at top dead center
with one hand while turning the nut of the
installing tool with the other. Operate the
installing tool until the crankshaft bottoms
against the bearing.
Before installing the crankshaft, clean the
contacting surface of crankcase.
CAUTION:
Do not use a hammer to drive in the crank-
shaft.
2. Check:
Shifter operation
Transmission operation
Unsmooth operation → Repair.
3. Install:
Oil strainer 1
Bolt (oil strainer) 2
4. Apply:
Sealant
On the crankcase (right) 1.
NOTE:
Clean the contacting surface of crankcase (left
and right) before applying the sealant.
Quick gasket®:
ACC-QUICK-GS-KT
YAMAHA Bond No. 1215:
90890-85505
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

4 - 91
ENGCRANKCASE AND CRANKSHAFT
5. Install:
Dowel pin 1
O-ring 2
Crankcase (right)
To crankcase (left).
NOTE:
Fit the crankcase (right) onto the crankcase
(left). Tap lightly on the case with soft ham-
mer.
When installing the crankcase, the connect-
ing rod should be positioned at TDC (top
dead center).
6. Tighten:
Hose guide 1
Clutch cable holder 2
Bolt (crankcase)
NOTE:
Tighten the crankcase tightening bolts in
stage, using a crisscross pattern.
7. Install:
Oil delivery pipe
O-ring
Bolt (oil delivery pipe)
8. Install:
Timing chain
Timing chain guide (rear)
Bolt (timing chain guide)
9. Remove:
Sealant
Forced out on the cylinder mating sur-
face.
10. Apply:
Engine oil
To the crank pin, bearing and oil deliv-
ery hole.
11. Check:
Crankshaft and transmission operation.
Unsmooth operation → Repair.
New
T R..12 Nm (1.2 m · kg, 8.7 ft · lb)
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)