engine YAMAHA WR 400F 2002 Owners Manual

ENG
4 - 84
CDI MAGNETO
EC4L0000
CDI MAGNETO
Extent of removal:1 CDI magneto removal
Extent of removal Order Part name Q’ty Remarks
CDI MAGNETO REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Bolt [radiator (left)]
Disconnect the CDI magneto
lead.Refer to “RADIATOR” section.
1 Engine guard (left) 1
2 Shift pedal 1
3 Crankcase cover (left) 1
4 Gasket 1
5 Dowel pin 2
6 Nut (rotor) 1 Use special tool.
Refer to “REMOVAL POINTS”.
7 Rotor 1
8 Stator 1
9Woodruff key
1
1

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ENG

CDI MAGNETO
4. Connect:

CDI magneto lead
Refer to “CABLE ROUTING DIA-
GRAM” section in the CHAPTER 2.
5. Install:

Gasket [crankcase cover (left)]

Crankcase cover (left)
1


Hose holder (cylinder head breather
hose)
2

Bolt [crankcase cover (left)]
NOTE:

Tighten the bolts in stage, using a crisscross
pattern.
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

6. Install:

Shift pedal
1


Bolt (shift pedal)
NOTE:

When installing the shift pedal onto the shift
shaft, be sure that the center of the shift pedal
is about 2 mm
a
above the top of the footrest.
7. Install:

Engine guard (left)
1


Hose holder (cylinder head breather
hose)
2

Bolt [engine guard (left)]
1
2
T R..23 Nm (2.3 m · kg, 17 ft · lb)

ENG
4 - 88
ENGINE REMOVAL
EC4M0000
ENGINE REMOVAL
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the frame.
WARNING
Support the machine securely so there is nodanger of it falling over.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Carburetor Refer to “CARBURETOR” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Clutch cable Disconnect at engine side.
Decompression cable and guide Disconnect at engine side.
Radiator Refer to “RADIATOR” section.
Shift pedal Refer to “CDI MAGNETO” section.
Cylinder head breather hose and
oil tank breather hoseRefer to “CAMSHAFTS” section.
Drain the engine oil Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Spark plug cap
Disconnect the CDI magneto lead.

ENG
4 - 89
ENGINE REMOVAL
Extent of removal:1 Engine removal
Extent of removal Order Part name Q’ty Remarks
1 Engine skidplate 1
2 Neutral switch 1
3 Oil hose 2
4 Chain cover 1
Refer to “REMOVAL POINTS”. 5 Nut (drive sprocket) 1
6 Lock washer 1
7 Drive sprocket 1
8 Clip 1
9 Bolt (brake pedal) 1
10 Brake pedal 1
11 Engine upper bracket (right) 1
12 Engine upper bracket (left) 1
13 Engine lower bracket 2
14 Engine mounting bolt 3
15 Pivot shaft 1
Refer to “REMOVAL POINTS”.
16 Engine 1
1

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ENGENGINE REMOVAL
EC4M3000
REMOVAL POINTS
EC4F3100
Drive sprocket
1. Remove:
Nut (drive sprocket) 1
Lock washer 2
NOTE:
Straighten the lock washer tab.
Loosen the nut while applying the rear brake.
2. Remove:
Drive sprocket 1
Drive chain 2
NOTE:
Remove the drive sprocket together with the
drive chain.
EC4M3301
Engine removal
1. Remove:
Pivot shaft 1
NOTE:
If the pivot shaft is pulled all the way out, the
swingarm will come loose. If possible, insert a
shaft of similar diameter into the other side of
the swingarm to support it.
2. Remove:
Engine 1
From right side.
NOTE:
Make sure that the couplers, hoses and cables
are disconnected.

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ENGENGINE REMOVAL
EC4M5000
ASSEMBLY AND INSTALLATION
EC4M5160
Engine installation
1. Install:
Engine 1
Install the engine from right side.
Pivot shaft 2
Engine mounting bolt (lower) 3
Engine lower bracket 4
Bolt (engine bracket) 5
Engine mounting bolt (front) 6
Engine upper bracket (right) 7
Engine upper bracket (left) 8
Bolt (engine bracket) 9
Engine mounting bolt (upper) 0
EC4M5211
Brake pedal
1. Install:
Spring
Brake pedal 1
O-ring 2
Bolt (brake pedal) 3
Clip 4
NOTE:
Apply the lithium soap base grease on the
bolt, O-rings and brake pedal bracket.
Install the clip with its stopper portion a fac-
ing inward.
T R..85 Nm (8.5 m · kg, 61 ft · lb)
T R..69 Nm (6.9 m · kg, 50 ft · lb)
T R..34 Nm (3.4 m · kg, 24 ft · lb)
T R..69 Nm (6.9 m · kg, 50 ft · lb)
T R..34 Nm (3.4 m · kg, 24 ft · lb)
T R..55 Nm (5.5 m · kg, 40 ft · lb)
New
T R..26 Nm (2.6 m · kg, 19 ft · lb)
Drive sprocket
1. Install:
Drive sprocket 1
Drive chain 2
NOTE:
Install the drive sprocket together with the
drive chain.

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ENGENGINE REMOVAL
2. Install:
Lock washer 1
Nut (drive sprocket) 2
NOTE:
Tighten the nut while applying the rear brake.
New
T R..75 Nm (7.5 m · kg, 54 ft · lb)
3. Bend the lock washer tab to lock the nut.
4. Install:
Chain guide
Chain cover 1
Screw (chain cover) 2
T R..8 Nm (0.8 m · kg, 5.8 ft · lb)
5. Install:
O-ring 1
Dowel pin 2
Oil hose 3
Bolt (oil hose) 4
NOTE:
Apply the lithium soap base grease on the O-
ring.
6. Install:
Spring 1
Pin 2
O-ring 3
Neutral switch 4
Screw (neutral switch) 5
NOTE:
Apply the lithium soap base grease on the O-
ring.
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
New
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)

ENG
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CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
Extent of removal:1 Crankcase separation2 Crankshaft removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE SEPARATION
Preparation for removal Engine Refer to “ENGINE REMOVAL” section.
Piston Refer to “CYLINDER AND PISTON” sec-
tion.
Balancer Refer to “BALANCER” section.
Kick axle assembly
Refer to “KICK AXLE AND SHIFT
SHAFT” section.
Segment
Stator Refer to “CDI MAGNETO” section.
1 Timing chain guide (rear) 1
2 Timing chain 1
3 Bolt (40 mm) 3
Refer to “REMOVAL POINTS”. 4 Bolt (50 mm) 4
5 Bolt (60 mm) 2
6 Bolt (75 mm) 3
7 Hose guide 1
8 Clutch cable holder 1
9 Crankcase (right) 1
10 Crankcase (left) 1
21

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ENGCRANKCASE AND CRANKSHAFT
REMOVAL POINTS
Crankcase
1. Separate:
Crankcase (right)
Crankcase (left)
Separation steps:
Remove the crankcase bolts, hose guide
and clutch cable holder.
NOTE:
Loosen each bolt 1/4 of a turn at a time and
after all the bolts are loosened, remove
them.
Remove the crankcase (right).
NOTE:
Place the crankcase with its left side
downward and split it by inserting a screw-
driver tip into the splitting slit a in the
crankcase.
Lift the crankcase (right) horizontally while
lightly patting the case splitting slit and
engine mounting boss using a soft ham-
mer, and leave the crankshaft and trans-
mission with the crankcase (left).
CAUTION:
Use soft hammer to tap on the case half.
Tap only on reinforced portions of case.
Do not tap on gasket mating surface.
Work slowly and carefully. Make sure the
case halves separate evenly. If one end
“hangs up”, take pressure off the push
screw, realign, and start over. If the
cases do not separate, check for a
remaining case screw or fitting. Do not
force.
Remove the dowel pins and O-ring.
a

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ENG
Crankshaft
1. Remove:
Crankshaft 1
Use the crankcase separating tool 2.
CAUTION:
Do not use a hammer to drive out the
crankshaft.
Crankshaft bearing
1. Remove:
Bearing 1
NOTE:
Remove the bearing from the crankcase by
pressing its inner race.
Do not use the removed bearing.
Crankcase separating tool:
YU-1135-A/90890-01135
INSPECTION
Timing chain and timing chain guide
1. Inspect:
Timing chain
Cracks/stiff → Replace the timing chain
and camshaft sprocket as a set.
2. Inspect:
Timing chain guide
Wear/damage → Replace.
EC4N4101
Crankcase
1. Inspect:
Contacting surface a
Scratches → Replace.
Engine mounting boss b, crankcase
Cracks/damage → Replace.
2. Inspect:
Bearing
Rotate inner race with a finger.
Rough spot/seizure → Replace.
3. Inspect:
Oil seal
Wear/damage → Replace.
CRANKCASE AND CRANKSHAFT