2008 YAMAHA YFZ450 engine

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dance with the periodic maintenance and lubrica-
tion chart. In addition, the condition of the spark
plug can reveal the condition of the engine.
To remove the spark plug
1. Remove the seat. (See page 4-11.)
2. Remove the bolts and the quick fastener
screws shown.
3. Remove the fuel tank cap by turning it coun-
terclockwise.
WARNING
EWB01870

Always turn off the engine before removing
the fuel tank cap.

Do not remove the fuel tank cap immediately
after the engine has been running and is still
very hot.

Do not spill gasoline on the engine, exhaust
pipe or muffler.

Never remove the fuel tank cap while smok-
ing, or in the vicinity of sparks, open flames,
or other sources of ignition such as the pilot
lights of water heaters and clothes dryers.
4. Pull the panel backward, and then remove the
panel.
5. Install the fuel tank cap by turning it clockwise.
6. Remove the bolt, lift the rear of the fuel tank,
and then tilt it back.
1. Panel
2. Bolt
3. Quick fastener screw
4. Fuel tank cap
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kit.
To check the spark plug
1. Check that the porcelain insulator around the
center electrode of the spark plug is a medi-
um-to-light tan (the ideal color when the ATV
is ridden normally).
NOTE:

If the spark plug shows a distinctly different color,
the engine could be operating improperly. Do not
attempt to diagnose such problems yourself. In-
stead, have a Yamaha dealer check the ATV.
2. Check the spark plug for electrode erosionand excessive carbon or other deposits, and
replace it if necessary.
To install the spark plug
1. Measure the spark plug gap with a wire thick-
ness gauge and, if necessary, adjust the gap
to specification.
1. Spark plug wrench
1

Specified spark plug:
NGK/CR8E
Spark plug gap:
0.7–0.8 mm (0.028–0.031 in)
1. Spark plug gap

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2. Clean the surface of the spark plug gasket
and its mating surface, and then wipe off any
grime from the spark plug threads.
3. Install the spark plug with the spark plug
wrench, and then tighten it to the specified
torque.
NOTE:

If a torque wrench is not available when installing
a spark plug, a good estimate of the correct torque
is 1/4–1/2 turn past finger tight. However, the spark
plug should be tightened to the specified torque as
soon as possible.
4. Install the spark plug cap.
5. Place the fuel tank in the original position, and
then install the bolt.
6. Remove the fuel tank cap by turning it coun-
terclockwise.
7. Place the panel in the original position.8. Install the fuel tank cap by turning it clockwise.
9. Install the bolts and the quick fastener screws.
10. Install the seat.
EBU23304
Engine oil and oil filter element
The engine oil level should be checked before
each ride. In addition, the oil must be changed and
the oil filter element replaced at the intervals spec-
ified in the periodic maintenance and lubrication
chart. Tightening torque:
Spark plug:
12.5 Nm (1.25 m·kgf, 9.0 ft·lbf)
1. Projection
2. Slot
21

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To check the engine oil level
1. Place the ATV on a level surface.
2. Start the engine, warm it up until the engine oil
has reached a normal temperature of 40 °C
(104 °F), let it continue to idle for ten seconds
or more, and then turn the engine off.
NOTE:

To achieve the proper engine oil temperature for
an accurate oil level reading, the engine must have
first completely cooled down, and then warmed up
again for several minutes to normal operating tem-
perature.
3. Remove the engine oil tank filler cap, wipe the
dipstick off with a clean rag.
4. Insert the dipstick into the filler hole (without
screwing it in), and then remove it again to
check the oil level.
NOTE:

The engine oil should be between the minimum
and maximum level marks.
5. If the engine oil is at or below the minimum
level mark, add sufficient oil of the recom-
mended type through the engine oil tank filler
hole to raise it to the correct level.
1. Engine oil tank filler cap
2. Dipstick
3. Engine oil tank
4. Engine oil filler cap
5. Maximum level mark
6. Minimum level mark
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NOTE:

When adding oil, be careful not to overfill the en-
gine oil tank; the oil level rises faster starting from
the half-level-portion on the dipstick.
6. Insert the dipstick into the engine oil tank filler
hole, and then tighten the engine oil tank filler
cap.
CAUTION:

ECB00360
Make sure that the engine oil tank filler cap is
securely tightened, otherwise oil may seep out
when the engine is running.
To change the engine oil (with or without oil
filter element replacement)
1. Place the ATV on a level surface.
2. Remove the engine guard by removing the
bolts.3. Start the engine, warm it up for several min-
utes, and then turn it off.
4. Place an oil pan under the engine to collect
the used oil.
5. Remove the crankcase engine oil filler cap
and the crankcase engine oil drain bolt.
1. Engine guard
2. Bolt
1
2

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6. Remove the engine oil tank filler cap and the
engine oil tank drain bolt.7. Check the washers for damage, and replace if
necessary.NOTE:

Skip steps 8–11 if the oil filter element is not being
replaced.
8. Remove the oil filter element cover by remov-
ing the bolts, and then remove the oil filter el-
ement.
1. Crankcase engine oil drain bolt
1

1. Engine oil tank drain bolt
1

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12. Install the crankcase engine oil drain bolt and
the engine oil tank drain bolt, and then tighten
them to the specified torques.
13. Pour the specified amount of the recommend-
ed engine oil through the engine oil tank filler
hole, and then install and tighten the engine oil
tank filler cap.
14. Pour the specified amount of the recommend-
ed engine oil through the crankcase engine oil
filler hole, and then install and tighten the
crankcase engine oil filler cap.NOTE:

Be sure to wipe off spilled oil on any parts after the
engine and exhaust system have cooled down.CAUTION:

ECB00300

In order to prevent clutch slippage (since the
engine oil also lubricates the clutch), do not
mix any chemical additives. Do not use oils
with a diesel specification of “CD” or oils of
a higher quality than specified. In addition,
Tightening torques:
Crankcase engine oil drain bolt:
20 Nm (2.0 m·kgf, 14 ft·lbf)
Engine oil tank drain bolt:
19 Nm (1.9 m·kgf, 14 ft·lbf)
Recommended oil:
See page 10-1.
Oil quantity:
Without oil filter element replacement:
Quantity in oil tank:
1.55 L (1.64 US qt) (1.36 Imp.qt)
Quantity in crankcase:
0.20 L (0.21 US qt) (0.18 Imp.qt)
With oil filter element replacement:
Quantity in oil tank:
1.55 L (1.64 US qt) (1.36 Imp.qt)
Quantity in crankcase:
0.30 L (0.32 US qt) (0.26 Imp.qt)

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do not use oils labeled “ENERGY CONSERV-
ING II” or higher.

Make sure that no foreign material enters the
crankcase.
15. Start the engine, and then let it idle for several
minutes while checking it for oil leakage. If oil
is leaking, immediately turn the engine off and
check for the cause.
16. Turn the engine off, and then check the oil lev-
el and correct it if necessary.
17. Install the engine guard by installing the bolts,
and then tighten them to the specified torque.
CAUTION:

ECB00370
Be sure to apply LOCTITE® to the engine
guard bolts before installing them.
EBU23470
Coolant
The coolant level should be checked before each
ride. In addition, the coolant must be changed atthe intervals specified in the periodic maintenance
and lubrication chart.
EBU23490
To check the coolant level
1. Place the ATV on a level surface.
NOTE:

The coolant level must be checked on a cold en-
gine since the level varies with engine tempera-
ture.
2. Check the coolant level in the coolant reser-
voir.
NOTE:

The coolant should be between the minimum and
maximum level marks. Tightening torque:
Engine guard bolt:
7 Nm (0.7 m·kgf, 5.1 ft·lbf)