engine YAMAHA YZ250LC 2002 Repair Manual

34 Nm (3.4 m•kg, 24 ft•lb)
4-60
ENGINE REMOVALENG
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for
Hold the machine by placing the
removalsuitable stand under the engine.
Seat and fuel tankRefer to “SEAT, FUEL TANK AND
SIDE COVERS” section.
Carburetor and carburetor jointRefer to “CARBURETOR AND REED
VALVE” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
Exhaust pipe stay (rear) SILENCER” section.
Clutch cable Disconnect at engine side.
Radiator Refer to “RADIATOR” section.
Spark plug
Disconnect the CDI magneto lead.
CDI unit
Reservoir tank (rear brake) Refer to “FRONT BRAKE AND REAR
BRAKE” section in the CHAPTER 5.
EC4M0000
ENGINE REMOVAL
w
Support the machine securely so there is no dan-
ger of it falling over.
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26 Nm (2.6 m•kg, 19 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
75 Nm (7.5 m•kg, 54 ft•lb)
8 Nm (0.8 m•kg, 5.8 ft•lb)
85 Nm (8.5 m•kg, 61 ft•lb)
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4-61
ENGINE REMOVALENG
Extent of removal:1Engine removal
Extent of removal Order Part name Q’ty Remarks
1 Chain cover 1
2 Nut (drive sprocket) 1
3 Lock washer 1 Refer to “REMOVAL POINTS”.
4 Drive sprocket 1
5 Clip 1
6 Bolt (brake pedal) 1
7 Brake pedal 1
8 Engine bracket 2
9 Engine mounting bolt 3
10 Pivot shaft 1 Remove completely.
11 Engine 1 Refer to “REMOVAL POINTS”.
1
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26 Nm (2.6 m•kg, 19 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
75 Nm (7.5 m•kg, 54 ft•lb)
8 Nm (0.8 m•kg, 5.8 ft•lb)
85 Nm (8.5 m•kg, 61 ft•lb)
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4-62
ENGINE REMOVALENG
EC4M3340
Engine removal
NOTE:
Make sure that the couplers, hoses and cables
are disconnected.
1. Lift the engine 1up to the point where the
engine’s mounting front does not contact the
bracket on the frame.
2. Remove the engine 1aslant and upward
while inclining it toward the kick crank side
so that the engine’s mounting top does not
contact the bracket on the frame.
EC4M3000
REMOVAL POINTS
EC4F3100
Drive sprocket
1. Remove:
9Nut (drive sprocket) 1
9Lock washer 2
NOTE:
9Straighten the lock washer tab.
9Loosen the nut while applying the rear brake.
2. Remove:
9Drive sprocket 1
9Drive chain 2
NOTE:
Remove the drive sprocket together with the
drive chain.
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4-63
ENGINE REMOVALENG
EC4M5341
Drive sprocket
1. Install:
9Drive sprocket 1
9Drive chain 2
NOTE:
Install the drive sprocket together with the drive
chain.
EC4M5211
Brake pedal
1. Install:
9Spring 1
9Brake pedal 2
9O-ring 3
9Bolt (brake pedal) 4
9Clip 5
NOTE:
9Apply the lithium soap base grease on the bolt,
O-rings and brake pedal bracket.
9Install the clip with its stopper portion afacing
inward.
EC4M5000
ASSEMBLY AND INSTALLATIONEC4M5123
Engine installation
1. Install:
9Engine 1
Install the engine from right side.
9Pivot shaft 2
9Engine mounting bolt (lower) 3
9Engine mounting bolt (front) 4
9Engine bracket 5
9Bolt (engine bracket) 6
9Engine mounting bolt (upper) 7
NOTE:
Apply the molybdenum disulfide grease on the
pivot shaft.
85 Nm (8.5 m•kg, 61 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
26 Nm (2.6 m•kg, 19 ft•lb)
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4-64
ENGINE REMOVALENG
4. Install:
9Chain guide 1
9Chain cover 2
9Screw (chain cover) 3 2. Install:
9Lock washer 1
9Nut (drive sprocket) 2
NOTE:
Tighten the nut while applying the rear brake.
3. Bend the lock washer tab to lock the nut.
8 Nm (0.8 m•kg, 5.8 ft•lb)
75 Nm (7.5 m•kg, 54 ft•lb)
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4-65
CRANKCASE AND CRANKSHAFTENG
Extent of removal Order Part name Q’ty Remarks
CRANKCASE AND CRANKSHAFT
REMOVAL
Preparation for Engine Refer to “ENGINE REMOVAL”section.
removal Piston Refer to “
CYLINDER HEAD, CYLINDER
AND PISTON
” section.
Primary drive gear
Kick idle gearRefer to “
KICK AXLE, SHIFT SHAFT AND
Stopper leverPRIMARY DRIVE GEAR”section.
Rotor and stator Refer to “CDI MAGNETO” section.
1 Segment 1 Refer to “REMOVAL POINTS”.
2 Bolt [L=50 mm (1.97 in)] 7
3 Bolt [L=60 mm (2.36 in)] 1
4 Bolt [L=70 mm (2.76 in)] 3
5 Holder 2
6 Crankcase (right) 1 Use special tool.
7 Crankcase (left) 1 Refer to “REMOVAL POINTS”.
8 Crankshaft 1 Use special tool.
Refer to “REMOVAL POINTS”.
9 Oil seal 2
10 Bearing 2 Refer to “REMOVAL POINTS”.
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EC4N0000
12
3
Extent of removal:1Crankcase separation2Crankshaft removal
3Crankshaft bearing removal
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10 Nm (1.0 m•kg, 7.2 ft•lb)30 Nm (3.0 m•kg, 22 ft•lb)
14 Nm (1.4 m•kg, 10 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
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4-66
CRANKCASE AND CRANKSHAFTENG
NOTE:
9Make appropriate bolts 3as shown available
by yourself and attach the tool with them.
9Fully tighten the tool holding bolts, but make
sure the tool body is parallel with the case. If
necessary, one screw may be backed out
slightly to level tool body.
9As pressure is applied, alternately tap on the
front engine mounting boss and transmission
shafts.
cC
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.
EC4N3000
REMOVAL POINTS
EC4N3100
Segment
1. Remove:
9Bolt (segment) 1
9Segment 2
NOTE:
Turn the segment counterclockwise until it stops
and loosen the bolt.
EC4N3212
Crankcase
1. Remove:
9Crankcase (right) 1
Use the crankcase separating tool 2.
Crankcase separating tool:
YU-1135-A/90890-01135
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4-67
CRANKCASE AND CRANKSHAFTENG
EC4N4000
INSPECTION
EC4N4101
Crankcase
1. Inspect:
9Contacting surface a
Scratches
Replace.
9Engine mounting boss b, crankcase
Cracks/Damage
Replace.
EC4N3401
Crankshaft bearing
1. Remove:
9Bearing 1
NOTE:
9Remove the bearing from the crankcase by
pressing its inner race as shown in å.
9If the bearing is removed together with the
crankshaft, remove the bearing using a general
bearing puller 2as shown in ∫.
9Do not use the removed bearing.
EC4N3302
Crankshaft
1. Remove:
9Crankshaft 1
Use the crankcase separating tool 2.
NOTE:
Make appropriate bolts 3as shown available by
yourself and attach the tool with them.
cC
Do not use a hammer to drive out the
crankshaft.
Crankcase separating tool:
YU-1135-A/90890-01135
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4-71
CRANKCASE AND CRANKSHAFTENG
8. Tighten:
9Segment 1
9Bolt (segment) 2
NOTE:
9When installing the segment onto the shift cam
3, align the punch mark awith the dowel pin
b.
9Turn the segment clockwise until it stops and
tighten the bolt.
30 Nm (3.0 m•kg, 22 ft•lb)
7. Install:
9Tension spring 1
9Holder 2
9Bolt (holder) 3
NOTE:
Install the holder so that it contacts the projec-
tion aon the crankcase (right).
10 Nm (1.0 m•kg, 7.2 ft•lb)
9. Remove:
9Sealant
Forced out on the cylinder mating surface.
10. Apply:
9Engine oil
To the crank pin, bearing, oil delivery hole
and connecting rod big end washer.
11. Check:
9Crankshaft and transmission operation
Unsmooth operation
Repair.
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4-72
TRANSMISSION, SHIFT CAM AND SHIFT FORKENG
Extent of removal Order Part name Q’ty Remarks
TRANSMISSION, SHIFT CAM AND
SHIFT FORK REMOVAL
Preparation for EngineRefer to “ENGINE REMOVAL” section.
removal Separate the crankcase. Refer to“CRANKCASE AND CRANK
SHAFT
” section.
1 Main axle 1
2 Drive axle 1
3 Shift cam 1
4 Shift fork 3 1Refer to “REMOVAL POINTS”.
5 Shift fork 2 1
6 Shift fork 1 1
7 Spacer 1
EC4H0000
Extent of removal:1Main axle, drive axle, shift cam and shift fork removal
1
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