2005 YAMAHA YFZ450 engine

6-3
EBU14120
Starting a cold engine
WARNING
_ 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. Apply the parking brake.
2. Turn the fuel cock to “ON”.
3. Turn the main switch to “ON” and the engine
stop switch to “RUN”.
4. Shift the transmission into neutral.
U5TG61.book Page 3 Friday, April 2, 2004 11:28 AM

6-5 1. Fully open 2. Half open
3. Closed a. Starter (choke)
1. Complètement ouvert 2. Mi- ouvert
3. Ferméa. Starter (enrichisseur)
1. Abre completamente 2. Semiabierto
3. Cerrado a. Arrancador (estrangulador)
NOTE:_ This model is equipped with an ignition circuit cut-
off system. The engine can be started under the
following conditions.

When the transmission is in neutral. At this
time the neutral indicator light should come
on. If the light does not come on, ask a
Yamaha dealer to inspect it.


When the clutch is disengaged with the trans-
mission in any position. However, it is recom-
mended to shift into neutral before starting
the engine.
_5. Use the starter (choke) in reference to the fig-
ure:
Position
1: Cold engine start-
ambient temperature below 5 °C.
Position
2: Cold engine start-
ambient temperature at 0 °C – 30°C
and warming up position.
Position
3: Cold engine start-
ambient temperature above 25°C
and warm engine start position.
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6-7
6. Completely close the throttle lever and start
the engine by pushing the start switch.NOTE:_ If the engine fails to start, release the start switch,
then push it again. Pause a few seconds before
the next attempt. Each cranking should be as short
as possible to preserve battery energy. Do not
crank the engine more than 10 seconds on each
attempt. _7. If the engine is started with the starter (choke)
in position
1, the starter (choke) should be
returned to position
2 to warm up the en-
gine. If the engine is started with the starter
(choke) in position
2, keep the starter
(choke) in this position to warm up the en-
gine.
8. Continue warming up the engine until it idles
smoothly and return the starter (choke) to po-
sition
3 before riding.CAUTION:_ See the “Engine break-in” section prior to op-
erating the engine for the first time. _
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6-9
EBU01800
Starting a warm engine
To start a warm engine, refer to the “Starting a cold
engine” section. The starter (choke) should not be
used. The throttle should be opened slightly.
EBU01820
Warming up
To get maximum engine life, always warm up the
engine before starting off. Never accelerate hard
with a cold engine! To see whether or not the en-
gine is warm, check if it responds to the throttle
normally with the starter (choke) turned off.
U5TG61.book Page 9 Friday, April 2, 2004 11:28 AM

6-11 1. Shift pedal N. Neutral position
1. Pédale de sélection N. Point mort
1. Pedal de cambios N. Posición de punto muerto
EBU01981
Shifting
This model has a 5-speed forward transmission.
The transmission allows you to control the amount
of power you have available at a given speed or for
starting, accelerating, climbing hills, etc. To shift
into neutral, return the throttle lever to its original
position, apply the clutch and repeatedly depress
the shift pedal until it stops. When it stops, it will be
in first gear. Raise the pedal slightly to neutral.CAUTION:_

Do not coast for long periods with the en-
gine off, and do not tow the machine a long
distance. Even in neutral position, the
transmission is only properly lubricated
when the engine is running. Inadequate lu-
brication may cause damage.


Always use the clutch when changing
gears. The engine, transmission and drive
train are not designed to withstand the
shock of forced shifting and can be dam-
aged by shifting without the clutch.
_
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6-13
EBU14260
To start out and accelerate:
1. Release the throttle lever, and then release
the parking brake.CAUTION:_ Always close the throttle while shifting gears.
Otherwise, damage to the engine and drive
train may result. _2. Pull the clutch lever to disengage the clutch.
3. Shift into first gear.
4. Open the throttle gradually and at the same
time, release the clutch lever slowly.
5. Once the machine has attained adequate
speed, release the throttle, and at the same
time, quickly pull in the clutch lever.
U5TG61.book Page 13 Friday, April 2, 2004 11:28 AM

6-17
EBU02080
To decelerate:
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 shift-
ing can cause the tires to lose traction, reducing
control and increasing the possibility of an acci-
dent.
WARNING
_ Make sure the engine has sufficiently slowed
before shifting to a lower gear. Engaging a low-
er gear when the engine speed is too high
could make the wheels stop rotating. This
could cause loss of control, an accident and
injury. It could also cause engine or drive train
damage. _
U5TG61.book Page 17 Friday, April 2, 2004 11:28 AM

6-19
EBU02092
Engine break-in
There is never a more important period in the life of
your machine than the period between zero and
20 hours.
For this reason, we ask that you carefully read the
following material. Because the engine is brand
new, you must not put an excessive load on it for
the first several hours of running. During the first
20 hours, the various parts in the engine wear and
polish themselves to the correct operating clear-
ances.
During this period, prolonged full throttle operation
or any condition which might result in excessive
engine heating must be avoided. However, mo-
mentary (2–3 seconds maximum) full throttle oper-
ation under load does not harm the engine. Each
full throttle acceleration sequence should be fol-
lowed with a substantial rest period for the engine
by cruising at lower r/min so the engine can rid it-
self of the temporary build up of heat.
If any abnormality is noticed during this period,
consult a Yamaha dealer.
U5TG61.book Page 19 Friday, April 2, 2004 11:28 AM