engine YAMAHA YZ250LC 2001 Service Manual

INSP
ADJ
3-11
AIR FILTER CLEANING
3. Install:
9Throttle cable cap
9Cap cover
EC35G040
AIR FILTER CLEANING
NOTE:
Proper air filter maintenance is the biggest key
to preventing premature engine wear and dam-
age.
cC
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.
1. Remove:
9Seat
9Fitting bolt 1
9Washer 2
9Air filter element 3
9Filter guide 4
2. Clean:
9Air filter element
Clean them with solvent.
NOTE:
After cleaning, remove the remaining solvent by
squeezing the element.
cC
Do not twist the element when squeezing
the element.
1 Nm (0.1 m•kg, 0.7 ft•lb)
5MW-9-30-3A 7/3/00 2:50 PM Page 30

INSP
ADJ
3-12
TRANSMISSION OIL LEVEL CHECK
3. Inspect:
9Air filter element
DamageÕReplace.
4. Apply:
9Foam-air-filter oil or engine mixing oil
To the element.
NOTE:
Squeeze out the excess oil. Element should be
wet but not dripping.
5. Install:
9Filter guide 1
NOTE:
Align the projection aon filter guide with the
hole bin air filter element.
6. Apply:
9Lithium soap base grease
On the matching surface aon air filter ele-
ment.
7. Install:
9Air filter element 1
9Washer
9Fitting bolt
NOTE:
Align the projection aon filter guide with the
hole bin air filter case.
EC35H002
TRANSMISSION OIL LEVEL CHECK
1. Start the engine, warm it up for several min-
utes and wait for five minutes.
2. Place the machine on a level place and hold
it up on upright position by placing the suit-
able stand under the engine.
2 Nm (0.2 m•kg, 1.4 ft•lb)
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INSP
ADJ
3-13
TRANSMISSION OIL REPLACEMENT
3. Check:
9Transmission oil level
EC35K002
TRANSMISSION OIL REPLACEMENT
1. Start the engine and warm it up for several
minutes and wait for five minute.
2. Place the machine on a level place and hold
it on upright position by placing the suitable
stand under the engine.
3. Place a suitable container under the engine.
Transmission oil level checking steps:
9Remove the oil check bolt 1.
9Inspect the oil level.
NOTE:
Be sure the machine is positioned straight
up when inspecting the oil level.
w
Never attempt to remove the oil check bolt
just after high speed operation. The heat-
ed oil could spout out, causing danger.
Wait until the oil cools down.
Oil flows outÕOil level is correct.
Oil does not flow outÕOil level is low.
Add transmission
oil until oil flows
out.
9Inspect the gasket (oil check bolt), replace if
damaged.
9Tighten the oil check bolt.
Recommended oil:
Yamalube 4 (10W-30) or SAE
10W-30 type SE motor oil
Oil check bolt:
10 Nm (1.0 m•kg, 7.2 ft•lb)
5MW-9-30-3A 7/3/00 2:51 PM Page 34

INSP
ADJ
3-15
IDLE SPEED ADJUSTMENT/MUFFLER INSPECTION/
SILENCER FIBER REPLACEMENT
EC35M001
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it up.
2. Adjust:
9Idle speed
EC35P010
MUFFLER INSPECTION
1. Inspect:
9O-ring 1
Damage ÕReplace.
EC35R041
SILENCER FIBER REPLACEMENT
1. Remove:
9Seat
9Side cover (right)
9Bolt (silencer) 1
9Silencer 2
9Bolt (fiber) 3 Adjustment steps:
Turn the throttle stop screw 1until the
engine runs at the lowest possible speed.
To increase idle speed ÕTurn the throttle
stop screw 1 1
in.
To decrease idle speed ÕTurn the throttle
stop screw 1 1
out.
5MW-9-30-3A 7/3/00 2:53 PM Page 38

3-25
DRIVE CHAIN SLACK ADJUSTMENT
INSP
ADJ
EC36A060
DRIVE CHAIN SLACK ADJUSTMENT
1. Elevate the rear wheel by placing the suit-
able stand under the engine.
2. Check:
9Drive chain slack a
Above the seal guard installation bolt.
Out of specification ÕAdjust
NOTE:
Before checking and/or adjusting, rotate the rear
wheel through several revolutions and check the
slack several times to find the tightest 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)
Drive chain lubricant:
SAE 10W-30 motor oil or suitable
chain lubricants
5. Install:
9Drive chain 1
9Joint 2
9Master link clip 3
cC
Be sure to install the master link clip to the
direction as shown.
aTurning direction
6. Lubricate:
9Drive chain
5MW-9-30-3B 7/3/00 3:23 PM Page 18

3-26
FRONT FORK INSPECTION
INSP
ADJ
3. Adjust:
9Drive chain slack
EC36C000
FRONT FORK INSPECTION
1. Inspect:
9Front fork smooth action
Operate the front brake and stroke the
front fork.
Unsmooth action/oil leakage ÕRepair or
replace.
Drive chain slack adjustment steps:
9Loosen the axle nut 1and locknuts 2.
9Adjust chain slack by turning the
adjusters 3.
To tighten ÕTurn adjuster 3 3
counter-
clockwise.
To loosen ÕTurn adjuster 3 3
clockwise
and push wheel forward.
9Turn each adjuster exactly the same amount
to maintain correct axle alignment. (There are
marks aon each side of chain puller align-
ment.)
NOTE:
Turn the adjuster so that the chain is in line
with the sprocket, as viewed from the rear.
cC
Too small chain slack will overload the
engine and other vital parts; keep the
slack within the specified limits.
9Tighten the axle nut while pushing down the
drive chain.
9Tighten the locknuts.
Axle nut:
125 Nm (12.5 m•kg, 90 ft•lb)
5MW-9-30-3B 7/3/00 3:23 PM Page 20

3-30
REAR SHOCK ABSORBER SPRING PRELOAD
ADJUSTMENTINSP
ADJ
EC36M013
REAR SHOCK ABSORBER SPRING
PRELOAD ADJUSTMENT
1. Elevate the rear wheel by placing the suit-
able stand under the engine.
2. Remove:
9Rear frame
3. Loosen:
9Locknut 1
4. Adjust:
9Spring preload
By turning the adjuster 2.
NOTE:
9Be sure to remove all dirt and mud from around
the locknut and adjuster before
adjustment.
9The length of the spring (installed) changes 1.5
mm (0.06 in) per turn of the adjuster.
cC
Never attempt to turn the adjuster beyond
the maximum or minimum setting.
5. Tighten:
9Locknut
6. Install:
9Rear frame
Stiffer ÕIncrease the spring preload.
(Turn the adjuster 2 2

in.)
Softer ÕDecrease the spring pre-
load. (Turn the adjuster 2 2
out.)
Extent of adjustment
242~260 mm
(9.53~10.24 in)
*257~275 mm
(10.12~10.83 in)
Spring length (installed) a a
:
Standard length
244 mm (9.61 in)
*267 mm (10.51 in)
*For EUROPE
29 Nm (2.9 m•kg, 21 ft•lb)
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3-35
STEERING HEAD INSPECTION AND ADJUSTMENT
INSP
ADJ
2. Inspect:
9Bearing free play
Exist play ÕReplace.
EC36U013
STEERING HEAD INSPECTION AND
ADJUSTMENT
1. Elevate the front wheel by placing a suitable
stand under the engine.
2. Check:
9Steering shaft
Grasp the bottom of the forks and gently
rock the fork assembly back and forth.
Free play ÕAdjust steering head.
3. Check:
9Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action ÕAdjust steering ring
nut.
4. Adjust:
9Steering ring nut
Steering ring nut adjustment steps:
9Remove the number plate.
9Remove the handlebar and handle crown.
9Loosen the ring nut 1using the ring nut
wrench 2.
9Tighten the ring nut 3using ring nut wrench
4.
NOTE:
Set the torque wrench to the ring nut wrench
so that they form a right angle.
Ring nut wrench:
YU-33975/90890-01403
5MW-9-30-3B 7/3/00 3:28 PM Page 38

3-38
ELECTRICAL/SPARK PLUG INSPECTION
INSP
ADJ
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
9Spark plug
2. Inspect:
9Electrode 1
Wear/Damage ÕReplace.
9Insulator color 2
Normal condition is a medium to light tan
color.
Distinctly different color ÕCheck the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure:
9Plug gap a
Use a wire gauge or thickness gauge.
Out of specification ÕRegap.
4. Clean the plug with a spark plug cleaner if
necessary.
5. Tighten:
9Spark plug
NOTE:
9Before installing a spark plug, clean the
gasket surface and plug surface.
9Finger-tighten athe spark plug before torquing
to specification b.
Spark plug gap:
0.5~0.6 mm (0.020~0.024 in)
Standard spark plug:
BR8EG (NGK)
20 Nm (2.0 m•kg, 14 ft•lb)
5MW-9-30-3B 7/3/00 3:30 PM Page 44

4-1
SEAT, FUEL TANK AND SIDE COVERSENG
EC400000
ENGINE
EC4R0000
SEAT, FUEL TANK AND SIDE COVERS
Extent of removal Order Part name Q’ty Remarks
SEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Preparation for Turn the fuel cock to “OFF”.
removal Disconnect the fuel hose.
1 Seat 1
2 Air scoop (left and right) 2
3 Fitting band 1 Remove on fuel tank side.
4 Bolt (fuel tank) 2
5 Fuel tank 1
6 Side cover (left) 1
Refer to “REMOVAL POINTS”.
7 Side cover (right) 1
8 Number plate 1
1
4
3
Extent of removal:1Seat removal2Fuel tank removal
3Side covers removal4Number plate removal
2
ü
ý
þ ü
ý
þ3
4
3 Nm (0.3 m•kg, 2.2 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
3 Nm (0.3 m•kg, 2.2 ft•lb)
3 Nm (0.3 m•kg, 2.2 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
5MW-9-30-4A 7/3/00 4:58 PM Page 2