2012 YAMAHA YFZ450R engine

7-6
7
opening, even when the throttle lever is pushed to
the maximum. Turning in the adjusting screw limits
the maximum engine power available and de-
creases the maximum speed of the ATV. Turning
in the adjusting screw decreases top speed, and
turning it out increases top speed. (See page 4-5.)
Loading and accessories
WARNING
EWB00972Improper loading or towing can increase the
risk of loss of control, an overturn, or other ac-
cident. To reduce the risk of an accident:

Do not exceed the maximum loading limits
for the vehicle (see “
MAXIMUM LOADING
LIMIT” below or vehicle labeling).
Make sure the load does not interfere with
your control or ability to see where you are
going.
Reduce speed and allow more room to stop.
A heavier vehicle takes longer to stop.
Avoid hills and rough terrain. Choose terrain
carefully. Use extreme caution when towing
or carrying a load on inclines.
Turn gradually and go slowly.As originally equipped, this ATV is not designed to
carry cargo or tow a trailer. If you choose to add ac-
cessories to carry cargo, you must use common
sense and good judgment.
Use extra caution when riding the ATV with addi-
tional loads, such as accessories or cargo. The
ATV’s handling may be adversely affected. Re-
duce your speed when adding additional loads.
1. Adjusting screw
2. Locknut
2
1
MAXIMUM LOADING LIMITATV loading limit (total weight of cargo, rider,
accessories, and tongue):100.0 kg (220 lb)
U18P66E0.book Page 6 Monday, May 16, 2011 4:23 PM

7-8
7
questions, consult an authorized ATV dealer.
WARNING! Operating this ATV with improper modifications may cause changes in handling
which in some situations could lead to an acci-
dent.
[EWB01491]
Exhaust system
WARNING
EWB01501
Dry grass or brush or other combustible ma-
terial accumulated around the engine area
could catch fire. Do not operate, idle, or park
the ATV in dry grass or other dry ground cov-
er. Keep the engine area free of dry grass,
brush, or other combustible material.
Someone touching the exhaust system dur-
ing or after operation could be burned. Do
not touch the hot exhaust system. Do not
park the ATV in a place where others might
be likely to touch it.The muffler and other engine parts become ex-
tremely hot during operation and remain hot after
the engine has stopped. To reduce the risk of fire
during operation or after leaving the ATV, do not let
brush, grass and other materials collect under the
vehicle, near the muffler or exhaust pipe, or next to other hot parts. Check under the vehicle after op-
erating in areas where combustible materials may
have collected. Do not idle or park the vehicle in
long dry grass or other dry ground cover.
To prevent burns, avoid touching the exhaust sys-
tem. Park the ATV in a place where pedestrians or
children are not likely to touch it.U18P66E0.book Page 8 Monday, May 16, 2011 4:23 PM

7-11
7Do not ride in areas posted “no trespassing ”.
Do not ride on private property without getting per-
mission. Select a large, flat, unpaved area to become famil-
iar with your ATV. Make sure that this area is free
of obstacles and other riders. You should practice
control of the throttle, brakes, shifting procedures,
and turning techniques in this area before trying
more difficult terrain.
Set the parking brake and follow the instruction on
page 6-1 to start the engine. Once it has warmed
up you are ready to begin riding your ATV. As you
get on the ATV, be sure not to accidentally move
the shift pedal. With the engine idling, pull the
clutch lever to disengage the clutch and shift into
1st gear, and then release the parking brake. Open
the throttle gradually, and at the same time, re-
lease the clutch lever slowly. Once the ATV has at-
tained adequate speed, release the throttle lever
and at the same time, quickly pull in the clutch le-
ver and shift into 2nd gear. Open the throttle part
way and gradually release the clutch.
WARNING!
If the throttle is applied too abruptly or if the
throttle is not released during shifting, or if the
shift pedal is not released before applying the
throttle, the front wheels may lift off the
ground, resulting in a loss of directional con-
U18P66E0.book Page 11 Monday, May 16, 2011 4:23 PM

7-12
7
trol.
[EWB02631]

NOTICE: Do not shift gears without
releasing the throttle. Damage to the engine or
drive train may occur.
[ECB01071]
Use this same procedure as you move into the
higher gears. Be sure to coordinate the use of the
throttle and shift pedal properly.
Avoid higher speeds until you are thoroughly famil-
iar with the operation of your ATV.
When slowing down or stopping, release the throt-
tle and apply the brakes smoothly and evenly. As
you slow down, shift to a lower gear. Be sure that
the engine has sufficiently slowed before engaging
a lower gear. Improper use of the brakes or shifting
can cause the tires to lose traction, reducing con-
trol and increasing the possibility of an accident.
TURNING YOUR ATV
WARNING
EWB01771Always follow proper procedures for turning
as described in this Owner ’s Manual. Practice
turning at low speeds before attempting to turn
at faster speeds. Do not turn at speeds too fast
for your skills or the conditions. ATV could go
out of control, causing a collision or overturn.
To achieve maximum traction on unpaved surfac-
es, the two rear wheels turn together at the same
speed. Therefore, unless the wheel on the inside
of the turn is allowed to slip or lose some traction,
the ATV will resist turning. A special turning tech-
nique must be used to allow the ATV to make turns
quickly and easily. It is essential that this skill be
learned first at low speed.
As you approach a curve, slow down and begin to
turn the handlebars in the desired direction. As you
do so, put your weight on the footrest to the outside
of the turn (opposite your desired direction) and
lean your upper body into the turn. Use the throttle
to maintain an even speed through the turn. This
maneuver will let the wheel on the inside of the turn
slip slightly, allowing the ATV to make the turn
properly.
U18P66E0.book Page 12 Monday, May 16, 2011 4:23 PM

8-1
8
EBU28783
PERIODIC MAINTENANCE AND ADJUSTMENT
EBU21674Periodic inspection, adjustment, and lubrication
will keep your vehicle in the safest and most effi-
cient condition possible. Safety is an obligation of
the vehicle owner/operator. The most important
points of vehicle inspection, adjustment, and lubri-
cation are explained on the following pages.
WARNING
EWB01841Failure to properly maintain the vehicle or per-
forming maintenance activities incorrectly may
increase your risk of injury or death during ser-
vice or while using the vehicle. If you are not fa-
miliar with vehicle service, have a Yamaha
dealer perform the service.
WARNING
EWB02562Turn off the engine when performing mainte-
nance unless otherwise specified.
A running engine has moving parts that can
catch on body parts or clothing and electri-
cal parts that can cause shocks or fires.

Running the engine while servicing can lead
to eye injury, burns, fire, or carbon monoxide
poisoning - possibly leading to death. See
page 2-3 for more information about carbon
monoxide.
WARNING
EWB02690Brake discs, calipers, drums, and linings can
become very hot during use. To avoid possible
burns, let brake components cool before
touching them.The intervals given in the periodic maintenance
charts should be considered as a general guide
under normal riding conditions. However, DE-
PENDING ON THE WEATHER, TERRAIN, GEO-
GRAPHICAL LOCATION, AND INDIVIDUAL
USE, THE MAINTENANCE INTERVALS MAY
NEED TO BE SHORTENED.
U18P66E0.book Page 1 Monday, May 16, 2011 4:23 PM

8-7
8
14*Chassis fasteners 
Make sure that all nuts, bolts, and screws are
properly tightened. √√√√√
15 *Shock absorber as-
semblies 
Check operation and correct if necessary.
 Check for oil leakage and replace if necessary. √√√
16 *Rear suspension re-
lay arm and con-
necting arm
pivoting points 
Check operation and correct if necessary. √√√√
17 *Steering shaft Lubricate with lithium-soap-based grease. √√√
18 *Steering system 
Check operation and repair or replace if damaged.
 Check toe-in and adjust if necessary. √√√√√
19 Engine oil 
Change.
 Check ATV for oil leakage, and correct if neces-
sary. √ √√√
20 Engine oil filter ele-
ment 
Replace. √√√
21 *Cooling system 
Check coolant level and ATV for coolant leakage,
and correct if necessary. √√√√√
 Replace coolant. Every 2 years
22 *Moving parts and
cables 
Lubricate. √√√√
NO. ITEM
CHECK OR MAINTENANCE
JOB INITIAL EVERY
Whichev- er comes first month136612
km
(mi) 320
(200) 1300
(800) 2500
(1600) 2500
(1600) 5000
(3200)
hours 20 80 160 160 320U18P66E0.book Page 7 Monday, May 16, 2011 4:23 PM

8-15
8
To install the cowling
1. Place the cowling in the original position, and
then tighten the quick fasteners.
2. Install panels C, B and A.EBU29441Checking the spark plug The spark plug is an important engine component,
which should be checked periodically, preferably
by a Yamaha dealer. Since heat and deposits will
cause any spark plug to slowly erode, the spark
plug should be removed and checked in accor-
dance with the periodic maintenance and lubrica-
tion chart. In addition, the condition of the spark
plug can reveal the condition of the engine.
The porcelain insulator around the center elec-
trode of the spark plug should be a medium-to-light
tan (the ideal color when the vehicle is ridden nor-
mally). If the spark plug shows a distinctly different
color, the engine could be operating improperly.
Do not attempt to diagnose such problems your-
self. Instead, have a Yamaha dealer check the ve-
hicle.
If the spark plug shows signs of electrode erosion
and excessive carbon or other deposits, it should
be replaced.
1. Quick fastener
1. Quick fastener
11
1
1
U18P66E0.book Page 15 Monday, May 16, 2011 4:23 PM

8-16
8Before installing the spark plug, the spark plug gap
should be measured with a wire thickness gauge
and, if necessary, adjusted to specification.
Clean the surface of the spark plug gasket and its
mating surface, and then wipe off any grime from
the spark plug threads.
TIPIf a torque wrench is not available when installing
the 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.EBU29499Engine 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.
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.
Specified spark plug:
NGK/CR8E
1. Spark plug gapSpark plug gap:0.7– 0.8 mm (0.028 –0.031 in)
Tightening torque:
Spark plug:13 Nm (1.3 m ·kgf, 9.4 ft ·lbf)
U18P66E0.book Page 16 Monday, May 16, 2011 4:23 PM