engine YAMAHA YZ250F 2006 Owner's Guide

3 - 1
INSP
ADJ
MAINTENANCE INTERVALS
EC300000
REGULAR INSPECTION AND ADJUSTMENTS
MAINTENANCE INTERVALS
The following schedule is intended as a general guide to maintenance and lubrication. Bear in mind
that such factors as weather, terrain, geographical location, and individual usage will alter the
required maintenance and lubrication intervals. If you are a doubt as to what intervals to follow in
maintaining and lubricating your machine, consult your Yamaha dealer.
ItemAfter
break-inEvery
race
Every
third
(or
500 km)Every
fifth
(or
1,000 km)As re-
quiredRemarks
ENGINE OIL
Replace
Inspect
OIL FILTER ELEMENT, OIL STRAINER
Clean
VALVES
The engine must be cold.
Check the valve seats
and valve stems for wear. Check the valve clearances
Inspect
Replace
VALVE SPRINGS
Check the free length and
the tilt. Inspect
Replace
VALVE LIFTERS
Check for scratches and
wear. Inspect
Replace
CAMSHAFTS Inspect the camshaft sur-
face.
Inspect the decompres-
sion system. Inspect
Replace
TIMING CHAIN SPROCKETS, TIMING
CHAIN
Check for wear on the
teeth and for damage. Inspect
Replace
PISTON
Inspect
Inspect crack
Inspect carbon deposits
and eliminate them. Clean
Replace
PISTON RING
InspectCheck ring end gap
Replace
PISTON PIN
Inspect
Replace
CYLINDER HEAD Inspect carbon deposits
and eliminate them.
Change gasket Inspect and clean
CYLINDER
Inspect and clean
Inspect score marks
Inspect wear
Replace
CLUTCH
Inspect housing, friction
plate, clutch plate and
spring Inspect and adjust
Replace
TRANSMISSION
Inspect
Replace bearing

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INSP
ADJ
PRE-OPERATION INSPECTION AND MAINTENANCE
EC320000
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap.
Check the cooling system for leakage.P.3-5 ~ 9
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the
fuel line for leakage.P.1-13
Engine oilCheck that the oil level is correct. Check the crankcase and oil
line for leakage.P.3-13 ~ 17
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-9 ~ 10
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-10 ~ 11
Brakes Check the play of front brake and effect of front and rear brake. P.3-23 ~ 29
Drive chainCheck drive chain slack and alignment. Check that the drive
chain is lubricated properly.P.3-30 ~ 32
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-40 ~ 41
SteeringCheck that the handlebar can be turned smoothly and have no
excessive play.P.3-41 ~ 43
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage. P.3-32 ~ 39
Cables (wires)Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or
when the front forks travel up and down.—
Exhaust pipeCheck that the exhaust pipe is tightly mounted and has no
cracks.P.4-3 ~ 5
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P.3-30
Lubrication Check for smooth operation. Lubricate if necessary. P.3-44
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-18
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-6
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs
before racing? Are inspection and maintenance completely
done?P.7-1 ~ 21

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INSP
ADJ
EC350000
ENGINE
COOLANT LEVEL INSPECTION
WARNING
Do not remove the radiator cap
1, drain
bolt and hoses when the engine and radia-
tor are hot. Scalding hot fluid and steam
may be blown out under pressure, which
could cause serious injury.
When the engine has cooled, place a thick
towel over the radiator cap, slowly rotate
the cap counterclockwise to the detent.
This procedure allows any residual pres-
sure to escape. When the hissing sound
has stopped, press down on the cap while
turning counterclockwise and remove it.
CAUTION:
Hard water or salt water is harmful to the
engine parts. You may use distilled water, if
you can’t get soft water.
1. Place the machine on a level place, and
hold it in an upright position.
2. Remove:
Radiator cap
3. Check:
Coolant level a
Coolant level low → Add coolant.
1Radiator
1a
ENGINE/COOLANT LEVEL INSPECTION

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INSP
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COOLANT REPLACEMENT
COOLANT REPLACEMENT
WARNING
Do not remove the radiator cap when the
engine is hot.
CAUTION:
Take care so that coolant does not splash
on painted surfaces. If it splashes, wash it
away with water.
1. Place a container under the engine.
2. Remove:
Coolant drain bolt 1
3. Remove:
Radiator cap
Drain the coolant completely.
4. Clean:
Cooling system
Thoroughly flush the cooling system with
clean tap water.
5. Install:
Copper washer
Coolant drain bolt
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
6. Fill:
Radiator
Engine
To specified level.
Recommended coolant:
High quality ethylene glycol
anti-freeze containing anti-
corrosion for aluminum engine
Coolant
1 and water (soft water)
2 mixing ratio:
50%/50%
Coolant capacity:
0.99 L (0.87 Imp qt, 1.05 US qt)

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INSP
ADJ
RADIATOR CAP INSPECTION
CAUTION:
Do not mix more than one type of ethyl-
ene glycol antifreeze containing corro-
sion inhibitors for aluminum engine.
Do not use water containing impurities or
oil.
7. Install:
Radiator cap
Start the engine and warm it up for a sev-
eral minutes.
8. Check:
Coolant level
Coolant level low → Add coolant. Handling notes of coolant:
The coolant is harmful so it should be han-
dled with special care.
WARNING
When coolant splashes to your eye.
Thoroughly wash your eye with water
and see your doctor.
When coolant splashes to your clothes.
Quickly wash it away with water and
then with soap.
When coolant is swallowed.
Quickly make him vomit and take him
to a doctor.
EC355000
RADIATOR CAP INSPECTION
1. Inspect:
Seal (radiator cap) 1
Valve and valve seat 2
Crack/damage → Replace.
Exist fur deposits 3 → Clean or replace.

3 - 10
INSP
ADJTHROTTLE CABLE ADJUSTMENT/
THROTTLE LUBRICATION
3. Install:
Cap 1
Boot 2
NOTE:
Place the tip a of the cap in the boot.
THROTTLE CABLE ADJUSTMENT
1. Check:
Throttle grip free play a
Out of specification → Adjust.
2. Adjust:
Throttle grip free play
Throttle grip free play
a:
3 ~ 5 mm (0.12 ~ 0.20 in)
Throttle grip free play adjustment steps:
Slide the adjuster cover.
Loosen the locknut 1.
Turn the adjuster 2 until the specified free
play is obtained.
Tighten the locknut.
T R..
Locknut:
4 Nm (0.4 m  kg, 2.9 ft  lb)
NOTE:
Before adjusting the throttle cable free play,
the engine idle speed should be adjusted.
WARNING
After adjusting, turn the handlebar to
right and left and make sure that the
engine idling does not run faster.
1 2
THROTTLE LUBRICATION
1. Remove:
Cover (throttle cable cap) 1
Cover (grip cap) 2
Throttle grip cap 3

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INSP
ADJHOT STARTER LEVER ADJUSTMENT/
AIR FILTER CLEANING
2. Apply:
Lithium soap base grease
On the throttle cable end a.
3. Install:
Throttle grip cap
Screw (throttle grip cap)
Cover (grip cap)
Cover (throttle cable cap)
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)
HOT STARTER LEVER ADJUSTMENT
1. Check:
Hot starter lever free play a
Out of specification → Adjust.
2. Adjust:
Hot starter lever free play
NOTE:
After adjustment, check proper operation of
hot starter.
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.
1. Remove:
Seat
Fitting bolt 1
Washer 2
Air filter element 3
Air filter guide 4
Hot starter lever free play
a:
3 ~ 6 mm (0.12 ~ 0.24 in)
Hot starter lever free play adjustment
steps:
Loosen the locknut 1.
Turn the adjuster 2 until free play a is
within the specified limits.
Tighten the locknut.

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INSP
ADJ
7. 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. Start the engine, warm it up for several
minutes, and then turn off the engine and
wait for five minutes.
2. Place the machine on a level place and
hold it up on upright position by placing the
suitable stand under the engine.
3. Inspect:
Oil level
Oil should be up to the full level in the
check window 1.
Level check window is not full. → Add
0.2 L (0.18 Imp qt, 0.21 US qt) of oil.
1
1
ENGINE OIL LEVEL INSPECTION

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INSP
ADJ
ENGINE OIL LEVEL INSPECTION
(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.
4. Install:
Oil tank cap
5. Start the engine and let it warm up for sev-
eral minutes.
6. Turn off the engine and inspect the oil level
once again.
NOTE:
Wait a few minutes until the oil settles before
inspecting the oil level.
Recommended oil:
At 5 °C (40 °F) or higher
È
Yamalube 4 (20W-40) or SAE
20W-40 type SG motor oil (Non-
Friction modified)
At 15 °C (60 °F) or lower
É
Yamalube 4 (10W-30) or SAE
10W-30 type SG 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 “SG” or higher grade
(Designed primarily for
motorcycles)-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

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INSP
ADJ
ENGINE OIL REPLACEMENT
ENGINE OIL REPLACEMENT
1. Start the engine and warm it up for several
minutes, and then turn off the engine 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.
4. Remove:
Lower engine guard 1
Bolt (oil tank) 2
Washer 3
Oil filler cap 4
Oil tank drain bolt 5
Crankcase oil drain bolt 6
Oil filter element drain bolt 7
Drain the crankcase and oil tank of its oil.
2
3
1
4
6
5
5. Remove:
Oil hose clamp 1
Bolt (oil hose)
Oil hose 2
Oil strainer 3
6. Inspect:
Oil strainer
Clogged → Blow.
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