engine oil YAMAHA WR 400F 2000 Owner's Manual

3 - 17
INSP
ADJENGINE OIL REPLACEMENT/
PILOT SCREW ADJUSTMENT
10. Install:
lOil filler plug
11. Inspect:
lEngine (for oil leaks)
lOil level
Refer to “ENGINE OIL LEVEL INSPEC-
TION”.
12. Check:
lOil pressure
PILOT SCREW ADJUSTMENT
1. Adjust:
lPilot screw 1
* Except for USAChecking steps:
lSlightly loosen the oil gallery bolt 1.
lStart 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.
lCheck oil passages, oil filter and oil pump
for damage or leakage.
lStart the engine after solving the prob-
lem(s) and recheck the oil pressure.
lTighten the oil gallery bolt to specification.
T R..
Oil gallery bolt:
18 Nm (1.8 m • kg, 13 ft • lb)
Adjusting steps:
lTurn in the pilot screw until it is lightly
seated.
lTurn out the pilot screw by the factory-set
number of turns.
Pilot screw:
1-5/8 turns out
* 1-1/2 turns out
(for reference only)
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.

3 - 33
INSP
ADJ
DRIVE CHAIN SLACK ADJUSTMENT
5. Install:
lDrive chain 1
lJoint 2
lMaster link clip 3
CAUTION:
Be sure to install the master link clip to the
direction as shown.
aTurning direction
6. Lubricate:
lDrive 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:
lDrive 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)

3 - 34
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.

ENG
4 - 20
CAMSHAFTS
CAMSHAFTS
CYLINDER HEAD COVER
Extent of removal:1 Cylinder head cover removal
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD COVER
REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Radiator Refer to “RADIATOR” section.
Carburetor Refer to “CARBURETOR” section.
1 Spark plug cap 1
2 Engine upper bracket (right) 1
3 Engine upper bracket (left) 1
4 Cylinder head breather hose 1
5 Oil tank breather hose 1
6 Bolt (cylinder head cover) 2
7 Cylinder head cover 1
8 Gasket 1
9 Timing chain guide (upper) 1
1

4 - 42
ENGCYLINDER AND PISTON
Piston pin
1. Inspect:
lPiston pin
Blue discoloration/grooves ®
Replace, then inspect the lubrication
system.
2. Measure:
lPiston pin-to-piston clearance
Measurement steps:
lMeasure the outside diameter (piston pin)
a.
If out of specification, replace the piston
pin
Outside diameter (piston pin):
17.991 ~ 18.000 mm
(0.7083 ~ 0.7087 in)
lMeasure the inside diameter (piston) b.
Inside diameter (piston):
18.004 ~ 18.015 mm
(0.7088 ~ 0.7093 in)
lCalculate the piston pin-to-piston clear-
ance with the following formula.
Piston pin-to-piston clearance =
Inside diameter (piston) b –
Outside diameter (piston pin) a
lIf out of specification, replace the piston.
Piston pin-to-piston clearance:
0.004 ~ 0.024 mm
(0.00016 ~ 0.00094 in)
: 0.07 mm (0.003 in)
ASSEMBLY AND INSTALLATION
Piston
1. Install:
lPiston rings
Onto the piston.
NOTE:
lBe sure to install the piston rings so that the
manufacturer’s marks or numbers are
located on the upper side of the rings.
lLubricate the piston and piston rings liberally
with engine oil.

4 - 43
ENGCYLINDER AND PISTON
2. Position:
lTop ring
l2nd ring
lOil ring
Offset the piston ring end gaps as
shown.
aTop ring end
b2nd ring end
cOil ring end (upper)
dOil ring
eOil ring end (lower)
3. Install:
lPiston 1
lPiston pin 2
lPiston pin clips 3
NOTE:
lApply engine oil onto the piston pin and pis-
ton.
lBe sure that the arrow mark a on the piston
points to the exhaust side of the engine.
lBefore installing the piston pin clip, cover the
crankcase with a clean rag to prevent the
piston pin clip from falling into the crankcase.
4. Lubricate:
lPiston
lPiston rings
lCylinder
NOTE:
Apply a liberal coating of engine oil.
Cylinder
1. Install:
lGasket 1
lCylinder 2
NOTE:
Install the cylinder with one hand while com-
pressing the piston rings with the other hand.
CAUTION:
lPass the timing chain 3 through the tim-
ing chain cavity.
lBe careful not to damage the timing chain
damper 4 during installation.
New
New

ENG
4 - 44
CLUTCH
CLUTCH
CLUTCH
Extent of removal:1 Push rod and push lever removal2 Push rod 1 disassembly
3 Friction plate and clutch plate removal4 Clutch housing removal
Extent of removal Order Part name Q’ty Remarks
CLUTCH REMOVAL
Preparation for removal Drain the engine oil. Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Brake pedal Refer to “ENGINE REMOVAL” section.
Clutch cable Disconnect at engine side.
1 Clutch cover 1
2 Gasket 1
3 Dowel pin 2
4 Clutch spring 5
5 Pressure plate 1
6 Push rod 1 1
7 Circlip 1
8 Plain washer 1
9 Bearing 1
10 Push rod 2 1
4
1
1
2
3

4 - 47
ENGCLUTCH
EC484500
Friction plate
1. Measure:
lFriction plate thickness
Out of specification ® Replace friction
plate as a set.
Measure at all four points.
EC484600
Clutch plate
1. Measure:
lClutch plate warpage
Out of specification ® Replace clutch
plate as a set.
Use a surface plate 1 and thickness
gauge 2.
Push lever
1. Inspect:
lPush lever 1
Wear/damage ® Replace.
Friction plate thickness:
Friction plate 1 [ø112 mm (4.41 in)]:
2.72 ~ 2.88 mm
(0.107 ~ 0.113 in)
: 2.5 mm (0.098 in)
Friction plate 2 [ø116 mm (4.57 in)]:
2.92 ~ 3.08 mm
(0.115 ~ 0.121 in)
: 2.7 mm (0.106 in)
Warp limit:
0.05 mm (0.002 in)
EC484810
Push rod
1. Inspect:
lPush rod 1 1
lBearing 2
lPlain washer 3
lPush rod 2 4
Wear/damage/bend ® Replace.
EC495000
ASSEMBLY AND INSTALLATION
Push lever
1. Install:
lPush lever 1
NOTE:
Apply the engine oil on the oil seal lip and push
lever.

4 - 48
ENGCLUTCH
EC495221
Clutch
1. Install:
lLock washer 1
lNut (clutch boss) 2
NOTE:
Use the clutch holding tool 3 to hold the clutch
boss.
For USA and CDN
õExcept for USA and CDN
Clutch holding tool:
YM-91042/90890-04086
New
T R..75 Nm (7.5 m · kg, 54 ft · lb)
õ
2. Bend the lock washer 1 tab.
3. Install:
lFriction plate 1 [ø112 mm (4.41 in)] 1
lClutch plate 2
lFriction plate 2 [ø116 mm (4.57 in)] 3
NOTE:
lInstall the clutch plates and friction plates
alternately on the clutch boss, starting with a
friction plate 1 and ending with a friction plate
2.
lApply the engine oil on the friction plates and
clutch plates.
4. Install:
lBearing 1
lPlain washer 2
lCirclip 3
To push rod 1 4.
NOTE:
Apply the engine oil on the bearing and plain
washer.
New

4 - 49
ENGCLUTCH
5. Install:
lPush rod 2 1
lPush rod 1 2
NOTE:
Apply the engine oil on the push rod 1, 2.
6. Install:
lPressure plate 1
NOTE:
Align the much mark a on the pressure plate
with the punched mark b on the clutch boss.
7. Install:
lClutch spring
lBolt (clutch spring)
NOTE:
Tighten the bolts in stage, using a crisscross
pattern.
T R..8 Nm (0.8 m · kg, 5.8 ft · lb)
8. Install:
lGasket (clutch cover) 1
lDowel pin 2
New
9. Install:
lClutch cover 1
lBolt (clutch cover)
NOTE:
Tighten the bolts in stage, using a crisscross
pattern.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)