engine YAMAHA WR 400F 2002 Workshop Manual

3 - 11
INSP
ADJ
THROTTLE LUBRICATION
2. Adjust:
Throttle grip free play
Throttle grip free play adjustment steps:
Remove the throttle cable cap 1 and
throttle cable cover 2.
NOTE:
Before adjusting the throttle cable free
play, the engine idle speed should be
adjusted.
When the motorcycle is accelerating,
throttle cable #1 3 is pulled and throttle
cable #2 4 is pushed.
1st step:
Loosen the locknuts 5 on throttle cable #2.
Adjust the free play by changing their
tightening position.
2nd step:
Loosen the locknuts 6 on throttle cable #1.
Adjust the free play by changing their
tightening position.
Tighten the locknuts.
WARNING
After adjusting, turn the handlebar to
right and left and make sure that the
engine idling does not run faster.
Install the throttle cable cover and throttle
cable cap.
1
2
THROTTLE LUBRICATION
1. Remove:
Cover (throttle cable cap) 1
Cover (grip cap) 2
Throttle cable cap 3
2. Apply:
Lithium soap base grease
On the throttle cable end a.
3. Install:
Throttle cable cap
Screw (throttle cable cap)
Cover (grip cap)
Cover (throttle cable cap)
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)

3 - 12
INSP
ADJDECOMPRESSION LEVER ADJUSTMENT/
AIR FILTER CLEANING
DECOMPRESSION LEVER ADJUSTMENT
1. Check:
Decompression lever free play
2. Adjust:
Decompression lever free play
AIR FILTER CLEANING
NOTE:
Proper air filter maintenance is the biggest key
to preventing premature engine wear and
damage.
CAUTION:
Never run the engine without the air filter
element in place; this would allow dirt and
dust to enter the engine and cause rapid
wear and possible engine damage.Checking steps:
Remove the timing plug.
Turn 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.
Check the free play c.
Free play:
5 ~ 9 mm (0.20 ~ 0.35 in)
Adjustment steps:
Loosen the locknut 1.
Turn the adjuster 2 in or out until the
adjustment is suitable.
Tighten 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 - 13
INSP
ADJ
1. Remove:
Seat
2. Disconnect:
Tail light lead connectors 1
3. Remove:
Air filter case cover 2
4. Remove:
Fitting bolt 1
Washer 2
Air filter element 3
Filter guide 4
5. Clean:
Air filter element
Clean them with solvent.
NOTE:
After cleaning, remove the remaining solvent
by squeezing the element.
CAUTION:
Do not twist the element when squeezing
the element.
Leaving too much of solvent in the ele-
ment may result in poor starting.
6. Inspect:
Air filter element
Damage → Replace.
7. Apply:
Foam-air-filter oil or engine mixing oil
To the element.
NOTE:
Squeeze out the excess oil. Element should be
wet but not dripping.
8. Install:
Filter guide 1
NOTE:
Align the projection a on filter guide with the
hole b in air filter element.
AIR FILTER CLEANING

3 - 14
INSP
ADJ
ENGINE OIL LEVEL INSPECTION
9. Apply:
Lithium soap base grease
On the matching surface a on air filter
element.
10. 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 - 15
INSP
ADJ
4. Inspect:
Oil level
Oil level should be between maximum
a and minimum b marks.
Oil level low → Add oil to proper level.
NOTE:
When inspecting the oil level, do not screw the
oil level gauge into the oil tank.
Insert the gauge lightly.
(For USA and CDN)
CAUTION:
Do not add any chemical additives.
Engine oil also lubricates the clutch and
additives could cause clutch slippage.
Do not allow foreign material to enter the
crankcase.
(Except for USA and CDN)
CAUTION:
Do not add any chemical additives or use
oils with a grade of CD a or higher.
Do not use oils labeled “ENERGY CON-
SERVING II” b or higher. Engine oil also
lubricates the clutch and additives could
cause clutch slippage.
Do not allow foreign materials to enter the
crankcase.
Recommended oil:
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 modified)
Recommended oil:
Refer to the following chart for
selection of oils which are suited
to the atmospheric temperatures.
Recommended engine oil classi-
fication:
API STANDARD:
API “SH” or higher grade
(Designed primarily for motor-
cycles)-20
-4-10
140
3010
5020
6830
8640 50
104
122°CTemp.
°F
10W-30
10W-40
20W-40
20W-50
15W-40
a
b
ENGINE OIL LEVEL INSPECTION

3 - 16
INSP
ADJ
ENGINE OIL REPLACEMENT
5. Start the engine and let it warm up for
several minutes.
CAUTION:
When the oil tank is empty, never start the
engine.
6. Idle the engine more than 10 seconds
while keeping the motorcycle upright.
Then stop the engine and add the oil to
the maximum level.
7. Install:
Oil tank cap
ENGINE OIL REPLACEMENT
1. Start the engine and let it warm up for
several minutes.
2. Stop the engine and place an oil pan
under the drain bolt.
3. Remove:
Oil filler plug 1
Drain bolt (with gasket) 2
Drain bolt (with gasket) 3
Oil filter drain bolt (O-ring) 4
Drain the crankcase and oil tank
(frame) of its oil.
4. Remove:
Engine skid plate
Engine oil hose clamp 1
Bolt (engine oil hose) 2
Engine oil hose 3
Oil strainer (frame) 4
5. Clean:
Oil strainer (frame)

3 - 17
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.
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)
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
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)
8. Install:
Gaskets
Oil filter drain bolt
Drain bolt (crankcase)
Drain bolt (frame)
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)
9. Fill:
Oil tank (frame)
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)

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INSP
ADJ
PILOT SCREW ADJUSTMENT
10. Install:
Oil filler plug
11. Inspect:
Engine (for oil leaks)
Oil level
Refer to “ENGINE OIL LEVEL INSPEC-
TION”.
12. Check:
Oil pressure
PILOT SCREW ADJUSTMENT
1. Adjust:
Pilot screw 1
* Except for USAChecking 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)
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:
WR426F: 1-5/8 turns out
* 1-1/8 turns out
WR400F: 1-1/2 turns out
(example)

3 - 19
INSP
ADJIDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
EC35M021
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it
up.
2. Adjust:
Idle speed
Adjustment steps:
Adjust the pilot screw.
Refer to “PILOT SCREW ADJUSTMENT”
section.
Turn the throttle stop screw 1 until the
engine runs at the lowest possible speed.
To increase idle speed →
Turn the throttle stop screw 1 in a.
To decrease idle speed →
Turn the throttle stop screw 1 out b.
Engine idling speed:
1,700 ~ 1,900 r/min
VALVE CLEARANCE ADJUSTMENT
NOTE:
The valve clearance should be adjusted
when the engine is cool to the touch.
The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
Seat
Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
2. Remove:
Carburetor
Refer to “CARBURETOR” section in
the CHAPTER 4.
Spark plug cap
Engine stay (upper)
Cylinder head cover
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
3. Remove:
Timing plug 1
Straight plug 2
O-ring

3 - 22
INSP
ADJ
VALVE CLEARANCE ADJUSTMENT
Round off the last digit of the installed pad
number to the nearest increment.
Last digit of pad
numberRounded value
0, 1 or 2 0
4, 5 or 6 5
8 or 9 10
EXAMPLE:
Installed pad number = 148
Rounded off value = 150
NOTE:
Pads can only be selected in 0.05 mm incre-
ments.
Locate the rounded-off value and the mea-
sured valve clearance in the chart “PAD
SELECTION TABLE”. The field where
these two coordinates intersect shows the
new pad number to use.
NOTE:
Use the new pad number only as a guide
when verifying the valve clearance adjust-
ment.
Install the new pads 0 and the valve lift-
ers A.
NOTE:
Apply the engine oil on the valve lifters.
Apply the molybdenum disulfide oil on the
valve stem ends.
Valve lifter must turn smoothly when
rotated with a finger.
Be careful to reinstall valve lifters and
pads in their original place.
Install the decompression shaft B, plain
washer C, bolt D, guide E, bolt F and
decompression cable G.
NOTE:
Apply the engine oil on the decompression
shaft.
T R..
Bolt (decompression shaft):
7 Nm (0.7 m • kg, 5.1 ft • lb)
Bolt (guide):
10 Nm (1.0 m • kg, 7.2 ft • lb)