2008 YAMAHA YFM50R engine

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EBU20682
Engine break-in
NOTE:


For ATVs equipped with an odometer or an hour
meter, follow the figures given in km (mi) or the
figures given in hours.

For ATVs not equipped with an odometer or
hour meter, follow the figures given in hours.
There is never a more important period in the life of
your engine than the first 320 km (200 mi) or 20
hours of riding. For this reason, you should read
the following material carefully.
Since the engine is brand new, do not put an ex-
cessive load on it for the first 320 km (200 mi) or 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 that might result in en-
gine overheating must be avoided.
0–160 km (0–100 mi) or 0–10 hours
Avoid prolonged operation above 1/2 throttle. Vary
the speed of the ATV regularly. Do not operate it at
one set throttle position.
160–320 km (100–200 mi) or 10–20 hours
Avoid prolonged operation above 3/4 throttle. Rev
the engine freely, but do not use full throttle at any
time.
320 km (200 mi) or 20 hours and beyond
The ATV can now be operated normally.CAUTION:

ECB00220
If any engine trouble should occur during the
engine break-in period, immediately have a
Yamaha dealer check the ATV.
EBU26770
Parking
When parking the ATV, stop the engine, shift the
drive select lever into the drive position, apply the
parking brake, and then turn the fuel cock to “OFF”.

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EBU20800
Parking on a slope
WARNING

EWB00880
Avoid parking on hills or other inclines. Park-
ing on a hill or other incline could cause the
ATV to roll out of control, increasing the
chance of an accident. If you must park on an
incline, place the ATV transversely across the
incline, shift the shift lever to the drive posi-
tion, stop the engine, apply the parking brake,
and then block the front and rear wheels with
rocks or other objects.
Do not park the ATV at all on hills that are so
steep you could not walk up them easily.
1. Bring the ATV to a stop by applying the brakes
in the drive position.
2. Stop the engine.
3. With the rear brake lever applied, apply the
parking brake and slowly release the brake le-
ver.
1. Parking brake lock plate
1. Locked position
1
1

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Not recommended for children under 6 years
of age.
WARNING

EWB01750
A child under 6 should never operate an ATV
with engine size greater than 50 cc. Use by chil-
dren of ATVs that are not recommended for
their age can lead to severe injury or death of
the child.This ATV is designed to carry operator only –
passengers prohibited.
WARNING
EWB01400
Never carry a passenger. The long seat is to al-
low the operator to shift position as needed
during operation. It is not for carrying passen-
gers. Carrying a passenger on this ATV greatly
reduces your ability to balance and control this
ATV. It could cause an accident, resulting in
harm to you and/or your passenger.

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Speed limiter
For riders less experienced with this model, the
throttle lever housing is equipped with a speed lim-
iter. The speed limiter keeps the throttle from fully
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.)
Yamaha recommends that all beginning riders
start off with the speed limiter turned in to limit the
amount of speed available while they learn. The
limiter may be gradually adjusted to increase max-
imum speed as the beginner becomes more famil-
iar with operating the ATV.
Loading and accessories
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
MAXIMUM LOADING LIMIT
ATV loading limit (total weight of cargo, rider,
accessories, and tongue):
40.0 kg (88 lb)
1

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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, and turning tech-
niques in this area before trying more difficult ter-
rain. Always avoid riding on paved surfaces: the
ATV is designed for use on unpaved surfaces only,
and handling maneuvers are more difficult to per-
form on pavement.
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. Re-
member that the engine and exhaust pipe will be
hot when riding and afterwards; do not allow skin
or clothing to come in contact with these compo-
nents.With the engine idling, shift the transmission into
the drive position and then release the parking
brake. Apply the throttle slowly and smoothly. The
centrifugal clutch will engage and you will start to
accelerate. If the throttle is applied too abruptly, the
front wheels may lift off the ground, resulting in a
loss of directional control. Avoid higher speeds un-
til you are thoroughly familiar with the operation of
your ATV.
When slowing down or stopping, release the throt-
tle and apply the brakes smoothly and evenly. Im-
proper use of the brakes can cause the tires to lose
traction, reducing control and increasing the possi-
bility of an accident.
TURNING YOUR ATV
To achieve maximum traction on unpaved surfac-
es, the two rear wheels are mounted solidly on one
axle and turn together at the same speed. There-
fore, unless the wheel on the inside of the turn is al-
lowed to slip or lose some traction, the ATV will
resist turning. A special turning technique 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.

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to continue up the hill, dismount the ATV on the up-
hill side. Physically turn the ATV around and then
descend the hill.
If you start to roll backwards, DO NOT apply the
rear brake to stop or try to put the ATV in gear. The
ATV could easily tip over backwards. Instead, ap-
ply the front brake gradually, or dismount the ATV
immediately on the uphill side.
WARNING

EWB01761
Maintain a steady speed when climbing a hill.
If you lose all forward speed:

Keep weight uphill.

Apply the brakes.

Lock the parking brake after you are
stopped.
If you begin rolling backwards:

Keep weight uphill.

Never apply the rear brake while rolling
backwards. Apply the front brake.

When fully stopped, apply the rear brake as
well, and then lock the parking brake.
Dismount on uphill side or to a side if pointed
straight uphill. Turn the ATV around and re-
mount, following the procedure described in
the Owner’s Manual.RIDING DOWNHILL
When riding your ATV downhill, shift your weight
as far to the rear and uphill side of the ATV as pos-
sible. Move back on the seat and sit with your arms
straight. Allow the engine compression to do most
of the braking for you. Improper braking may cause
a loss of traction.
Use caution while descending a hill with loose or
slippery surfaces. Braking ability and traction may
be adversely affected by these surfaces. Improper
braking may also cause a loss of traction.
Whenever possible, ride your ATV straight down-

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EBU28781
PERIODIC MAINTENANCE AND MINOR REPAIR
EBU21670
Safety is an obligation of the owner. Periodic in-
spection, adjustment and lubrication will keep your
ATV in the safest and best operating condition
possible. The most important points of inspection,
adjustment, and lubrication are explained on the
following pages.
The intervals given in the periodic maintenance
and lubrication chart should be considered as a
general guide under normal riding conditions.
However, DEPENDING ON THE WEATHER,
TERRAIN, GEOGRAPHICAL LOCATION, AND
INDIVIDUAL USE, THE MAINTENANCE INTER-
VALS MAY NEED TO BE SHORTENED.
WARNING

EWB01840
Never service an engine while it is running.
Moving parts can catch clothing or parts of the
body, causing injury. Electrical components
can cause shocks or start fires. Turn off the en-
gine when performing maintenance unless
otherwise specified. Have a Yamaha dealer
perform the service if you are not familiar with
maintenance work.
EBU27110
Owner’s manual and tool kit
Be sure to put this owner’s manual in the plastic
bag and to always carry it as well as the owner’s
tool kit and the low-pressure tire gauge in their re-
spective compartments under the seat.
1. Owner’s manual
2. Low-pressure tire gauge
3. Owner’s tool kit3
1
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EBU21742
Periodic maintenance chart for the emission control system
NOTE:


For ATVs not equipped with an odometer or an hour meter, follow the month maintenance intervals.

For ATVs equipped with an odometer or an hour meter, follow the km (mi) or hours maintenance inter-
vals. However, keep in mind that if the ATV isn’t used for a long period of time, the month maintenance
intervals should be followed.

Items marked with an asterisk should be performed by a Yamaha dealer as they require special tools,
data and technical skills.
NO. ITEMCHECK OR MAINTENANCE
JOBINITIAL EVERY
Whichev-
er comes
firstmonth 1 3 6 6 12
km
(mi)320
(200)1300
(800)2500
(1600)2500
(1600)5000
(3200)
hours 20 80 160 160 3201
*
Fuel line


Check fuel hoses for cracks or other damage, and
replace if necessary.
√√√
2 Spark plug

Check condition and clean, regap, or replace if
necessary.
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*
Valves


Check valve clearance and adjust if necessary.
√ √√√
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*
Carburetor


Check choke operation and correct if necessary.

Check engine idling speed and adjust if neces-
sary.
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*
Crankcase breather
system


Check breather hose for cracks or other damage,
and replace if necessary.
√√√