engine YAMAHA YFZ450R 2011 Service Manual

8-26
87. Start the engine and rev it up approximately
twenty times while momentarily creating ex-
haust system back pressure by blocking the
end of the muffler with a shop towel.
8. Stop the engine and allow the exhaust pipe to
cool.
9. Check the gasket for damage, and replace it if
necessary.
10. Install the gasket and the purging bolt, and
then tighten the bolt to the specified torque.
WARNING
EWB02380Never run the engine in an enclosed area when
purging the spark arrester, otherwise it could
cause injury to the eyes, burns, carbon monox-
ide poisoning, possibly leading to death, and
start a fire.
Always let the exhaust system cool prior to
touching exhaust components.
Always wear eye protection, and make sure
no one is behind the ATV.
Make sure there are no combustible materi-
als in the area.EBU29701Adjusting the throttle lever free play The throttle lever free play should be checked and,
if necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
1. Purging bolt
2. Gasket
2
1
Tightening torque:
Purging bolt:
27 Nm (2.7 m·kgf, 20 ft·lbf)
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8-27
8 The throttle lever free play should measure 2.0–
4.0 mm (0.08–0.16 in) at the throttle lever. Period-
ically check the throttle lever free play and, if nec-
essary, adjust it as follows.
1. Slide the rubber cover back.
2. Loosen the locknut.
3. To increase the throttle lever free play, turn
the throttle lever free play adjusting bolt in di-
rection (a). To decrease the throttle lever free
play, turn the adjusting bolt in direction (b).
4. Tighten the locknut.5. Slide the rubber cover to its original position.
EBU24060Valve clearance The valve clearance changes with use, resulting in
improper air-fuel mixture and/or engine noise. To
prevent this from occurring, the valve clearance
must be adjusted by a Yamaha dealer at the inter-
vals specified in the periodic maintenance and lu-
brication chart.EBU29601Brakes Replacement of brake components requires pro-
fessional knowledge. Brake service should be per-
formed by a Yamaha dealer.
WARNING
EWB02571Operating with improperly serviced or adjust-
ed brakes could lead to a loss in braking ability
and an accident.EBU24130Checking the front and rear brake pads The front and rear brake pads must be checked for
wear at the intervals specified in the periodic main-
tenance and lubrication chart.
1. Rubber cover
2. Throttle lever free play adjusting bolt
3. Locknut
4. Throttle lever free play
3 2
4 (a)(b)
1
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8-35
8 3. If the drive chain slack is incorrect, adjust it as
follows.
To adjust the drive chain slack
1. Place the ATV on a level surface.
2. Loosen the rear wheel axle pinch bolts.
3. Insert a rod of a diameter of 8 mm (0.3 in) and
a length of 10 cm (4 in) into one of the holes in
the drive chain tensioner as shown.
TIPA rod can be obtained at a Yamaha dealer to make
this adjustment.4. Shift the transmission into neutral.
5. To tighten the drive chain, push the ATV back-
ward. To loosen the drive chain, push the ATV
forward. NOTICE: Improper drive chain
slack will overload the engine as well as
other vital parts of the ATV and can lead to
drive chain slippage or breakage. To pre-
1. Drive chain slack
1
1. Rear wheel axle pinch bolt
2. Rod
3. Drive chain tensioner
4. Hole
3
4
2
1
1
U18P64E0.book Page 35 Thursday, May 13, 2010 6:00 PM

8-37
8 2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a
special O-ring chain lubricant. NOTICE: Do
not use engine oil or any other lubricants
for the drive chain, as they may contain
substances that could damage the O-
rings.
[ECB00581]
EBU24901
Checking and lubricating the cables The operation and the condition of all control ca-
bles should be checked before each ride, and the
cables and cable ends should be lubricated if nec-essary. If a cable is damaged or does not move
smoothly, have a Yamaha dealer check or replace
it.
WARNING
EWB02581
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the cable
sheaths become damaged, and cables can
also become frayed or kinked, which could
restrict the operation of controls and lead to
an accident or injury.
Always make sure all control cables work
smoothly before you begin riding in cold
weather. If the control cables are frozen or do
not work smoothly, you could be unable to
control the ATV, which could lead to an acci-
dent or collision.
1. O-rings
1 1
Recommended lubricant:
Engine oil
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8-50
8
EBU27691Troubleshooting charts Starting problems or poor engine performance
Check the fuel level in
the fuel tank.1. Fuel
There is enough fuel.
There is no fuel.
Check the compression.
Supply fuel.
The engine does not start.
Check the compression.
Operate the electric starter.2. Compression
There is compression.
There is no compression.
Check the ignition.
Have a Yamaha dealer
check the ATV.
Remove the spark plug
and check the electrodes.3. Ignition
Wipe off with a dry cloth and correct the
spark plug gap, or replace the spark plug.
Have a Yamaha dealer check the ATV.
The engine does not start.
Have a Yamaha dealer
check the ATV.
The engine does not start.
Check the battery.
Operate the electric starter.4. Battery
The engine turns over
quickly.
The engine turns over
slowly.
The battery is good.Check the battery lead connections,
and charge the battery if necessary.
DryWet
Operate the electric starter.
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8-51
8 Engine overheating
WARNING
EWB02290Wait for the engine and radiator to cool before removing the radiator cap. You could be burned by
hot fluid and steam blown out under pressure. Always put a thick rag over the cap when opening.
Allow any remaining pressure to escape before completely removing the cap.TIPIf coolant is not available, tap water can be temporarily used instead, provided that it is changed to the rec-
ommended coolant as soon as possible.Wait until the
engine has cooled.
Check the coolant level in the
reservoir and radiator.
The coolant level
is OK.The coolant level is low.
Check the cooling system
for leakage.
Have a Yamaha dealer check
and repair the cooling system.Add coolant. (See TIP.)
Start the engine. If the engine overheats again, have a
Yamaha dealer check and repair the cooling system.
There is
leakage.
There is
no leakage.
U18P64E0.book Page 51 Thursday, May 13, 2010 6:00 PM

9-1
9
EBU25860
CLEANING AND STORAGE
EBU25902Cleaning Frequent, thorough cleaning of your ATV will not
only enhance its appearance but will improve its
general performance and extend the useful life of
many components.
1. Before cleaning the ATV:
a. Block off the end of the exhaust pipe to
prevent water entry. A plastic bag and
strong rubber band may be used.
b. Make sure the spark plug and all filler caps
are properly installed.
2. If the engine case is excessively greasy, apply
degreaser with a paint brush. Do not apply de-
greaser to the chain, sprockets or wheel ax-
les.
3. Rinse the dirt and degreaser off with a garden
hose. Use only enough pressure to do the job.
WARNING! Wet brakes may have reduced
stopping ability, increasing the chance of
an accident. Test the brakes after washing.
Apply the brakes several times at slow
speeds to let friction dry out the linings.
[EWB02311]
NOTICE: Excessive water pressuremay cause water seepage and deteriora-
tion of wheel bearings, brakes, transmis-
sion seals and electrical devices. Many
expensive repair bills have resulted from
improper high-pressure detergent applica-
tions such as those available in coin-oper-
ated car washers.
[ECB00711]
4. Once most of the dirt has been hosed off,
wash all surfaces with warm water and mild,
detergent-type soap. An old toothbrush or bot-
tle brush is handy for hard-to-reach places.
5. Rinse the ATV off immediately with clean wa-
ter and dry all surfaces with a chamois, clean
towel or soft absorbing cloth.
6. Dry the chain and lubricate it to prevent it from
rusting.
7. Clean the seat with a vinyl upholstery cleaner
to keep the cover pliable and glossy.
8. Automotive type wax may be applied to all
painted and chrome plated surfaces. Avoid
combination cleaner-waxes. Many contain
abrasives which may mar the paint or protec-
tive finish. When finished cleaning, start the
engine and let it idle for several minutes.
U18P64E0.book Page 1 Thursday, May 13, 2010 6:00 PM

9-2
9
EBU27261Storage Short-term
Always store your ATV in a cool, dry place and, if
necessary, protect it against dust with a porous
cover. NOTICE: Storing the ATV in a poorly ven-
tilated room or covering it with a tarp while it is
still wet, will allow water and humidity to seep
in and cause rust. To prevent corrosion, avoid
damp cellars, stables (because of the presence
of ammonia) and areas where strong chemi-
cals are stored.
[ECB00721]
Long-term
Before storing your ATV for several months:
1. Follow all the instructions in the “Cleaning”
section of this chapter.
2. Fill up the fuel tank and add fuel stabilizer (if
available) to prevent the fuel from deteriorat-
ing.3. Perform the following steps to protect the cyl-
inder, piston rings, etc. from corrosion.
a. Remove the spark plug cap and spark
plug.
b. Pour a teaspoonful of engine oil into the
spark plug bore.
c. Install the spark plug cap onto the spark
plug, and then place the spark plug on the
cylinder head so that the electrodes are
grounded. (This will limit sparking during
the next step.)
d. Turn the engine over several times with the
starter. (This will coat the cylinder wall with
oil.)
e. Remove the spark plug cap from the spark
plug, and then install the spark plug and
the spark plug cap.
4. Lubricate all control cables and the pivoting
points of all levers and pedals.
5. Check and, if necessary, correct the tire air
pressure, and then block up the ATV so that
all of its wheels are off the ground. Alternative-
ly, turn the wheels a little every month in order
to prevent the tires from becoming degraded
in one spot. Specified amount:
7.5 ml of stabilizer to each liter of fuel (or 1
oz of stabilizer to each gallon of fuel)U18P64E0.book Page 2 Thursday, May 13, 2010 6:00 PM

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10
EBU25960
SPECIFICATIONS
Dimensions:Overall length:
1795 mm (70.7 in)
Overall width:
1240 mm (48.8 in)
Overall height:
1065 mm (41.9 in)
Seat height:
810 mm (31.9 in)
Wheelbase:
1270 mm (50.0 in)
Ground clearance:
235 mm (9.3 in)
Minimum turning radius:
3600 mm (142 in)Weight:With oil and fuel:
184.0 kg (406 lb)Noise and vibration level:Noise level (77/311/EEC):
84.5 dB(A) (EUR)(FRA)(GBR)
Vibration on seat (EN1032, ISO5008):
Will not exceed 0.5 m/s² (EUR)(FRA)(GBR)
Vibration on handlebar (EN1032, ISO5008):
Will not exceed 2.5 m/s² (EUR)(FRA)(GBR)Engine:Engine type:
Liquid cooled 4-stroke, DOHCCylinder arrangement:
Forward-inclined single cylinder
Displacement:
449 cm³
Bore × stroke:
95.0 × 63.4 mm (3.74 × 2.50 in)
Compression ratio:
11.40 :1
Starting system:
Electric starter
Lubrication system:
Dry sump
Engine oil:Recommended brand:
YAMALUBE
U18P64E0.book Page 1 Thursday, May 13, 2010 6:00 PM

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10
Type:
SAE 5W-30, 10W-30, 10W-40, 15W-40, 20W-40 or 20W-
50
Recommended engine oil grade:
API service SG type or higher, JASO standard MA
Engine oil quantity:
Without oil filter element replacement:
1.40 L (1.48 US qt, 1.23 Imp.qt)
With oil filter element replacement:
1.45 L (1.53 US qt, 1.28 Imp.qt)Cooling system:Coolant reservoir capacity (up to the maximum level mark):
0.25 L (0.26 US qt, 0.22 Imp.qt)
Radiator capacity (including all routes):
1.25 L (1.32 US qt, 1.10 Imp.qt)
Air filter:Air filter element:
Wet elementFuel:Recommended fuel:
Premium unleaded gasoline only
Fuel tank capacity:
10.0 L (2.64 US gal, 2.20 Imp.gal)
Fuel reserve amount:
3.4 L (0.90 US gal, 0.75 Imp.gal)Fuel injection:Throttle body:
ID mark:
18P1 00Spark plug (s):Manufacturer/model:
NGK/CR8E
Spark plug gap:
0.7–0.8 mm (0.028–0.031 in)Clutch:Clutch type:
Wet, multiple-discTransmission:Primary reduction system:
Spur gear
Primary reduction ratio:
61/23 (2.652)
Secondary reduction system:
Chain drive
Secondary reduction ratio:
38/14 (2.714)
-20 -10 0
1020 304050 ˚C
SAE 15W-40
SAE 20W-40SAE 20W-50
SAE 10W-40
SAE 5W-30
SAE 10W-30
U18P64E0.book Page 2 Thursday, May 13, 2010 6:00 PM