engine YAMAHA YFM50R 2007 Owner's Guide

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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-hill. Avoid sharp angles which could allow the ATV
to tip or roll over. Carefully choose your path and
ride no faster than you will be able to react to ob-
stacles which may appear.
WARNING
EWB01620
Always follow proper procedures for going
down hills as described in this Owner’s Manu-
al.
Note: a special technique is required when
braking as you go down a hill.

Always check the terrain carefully before
you start down any hill.

Shift your weight backward.

Never go down a hill at high speed.

Avoid going down a hill at an angle that
would cause the ATV to lean sharply to one
side. Go straight down the hill where possi-
ble.

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EBU21653
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
2

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*
Rear brake

Check operation and correct if necessary.

Check brake lever free play and adjust if neces-
sary.
√√√√√

Replace brake shoes. Whenever worn to the limit
8
*
Wheels

Check runout and for damage, and replace if nec-
essary.
√ √√√
9
*
Tires


Check tread depth and for damage, and replace if
necessary.

Check air pressure and balance, and correct if
necessary.
√ √√√
10
*
Wheel bearings


Check for looseness or damage, and replace if
necessary.
√ √√√
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*
Drive shaft univer-
sal joint


Lubricate with lithium-soap-based grease.
√√√
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*
Chassis fasteners


Make sure that all nuts, bolts, and screws are
properly tightened.
√√√√√
13
*
Shock absorber
assemblies


Check operation and correct if necessary.

Check for oil leakage and replace if necessary.
√√√
14
*
Knuckle shafts


Lubricate with lithium-soap-based grease.
√√√
15
*
Steering shaft


Lubricate with lithium-soap-based grease.
√√√
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*
Steering system


Check operation and repair or replace if damaged.

Check toe-in 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.
√√√√
NO. ITEMCHECK OR MAINTENANCE
JOBINITIAL EVERY
Whichev-
er comes
firstmonth 1 3 6 6 12
km
(mi)320
(200)1200
(750)2400
(1500)2400
(1500)4800
(3000)
hours 20 75 150 150 300

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18
*
Crankcase breather
system

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

Change.

Check ATV for oil leakage, and correct if neces-
sary.
√ √√√
20 Final gear oil

Change.

Check ATV for oil leakage, and correct if neces-
sary.
√√
21
*
Moving parts and
cables


Lubricate.
√√√√
22
*
Throttle lever hous-
ing and cable


Check operation and correct if necessary.

Check throttle cable free play and adjust if neces-
sary.

Lubricate throttle lever housing and cable.
√√√√√
23
*
Exhaust system


Check for leakage and replace gasket(s) if neces-
sary.

Check for looseness and tighten all screw clamps
and joints if necessary.
√√√
24 Spark arrester

Clean.
√√√
25
*
Front and rear brake
switches


Check operation and correct if necessary.
√√√√√
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*
Battery


Check electrolyte level and specific gravity, and
correct if necessary.

Make sure that the breather hose is properly
routed.
√√√√√
NO. ITEMCHECK OR MAINTENANCE
JOBINITIAL EVERY
Whichev-
er comes
firstmonth136612
km
(mi)320
(200)1200
(750)2400
(1500)2400
(1500)4800
(3000)
hours 20 75 150 150 300

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EBU23211
Checking the spark plug
The spark plug is an important engine component,
which is easy to check. 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.
To remove the spark plug
1. Remove the spark plug cap.
2. Remove the spark plug as shown, with thespark plug wrench included in the owner’s tool
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.
1. Spark plug cap
1

1. Spark plug wrench
1

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2. Check the spark plug for electrode erosion
and 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.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.
EBU23251
Engine oil
The engine oil level should be checked before
each ride. In addition, the oil must be changed at
the intervals specified in the periodic maintenance
and lubrication chart. Specified spark plug:
NGK/CR7HSA
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
1. Spark plug gap
Tightening torque:
Spark plug:
12.5 Nm (1.25 m·kgf, 9.0 ft·lbf)

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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 for several min-
utes, and then turn it off.
3. Wait a few minutes until the oil settles before
checking.
4. Remove the engine oil filler cap, and then
wipe the dipstick off with a clean rag.
5. 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.
6. If the engine oil is at or below the minimum
level mark, add sufficient oil of the recom-
mended type to raise it to the correct level.
7. Insert the dipstick into the oil filler hole, and
then tighten the engine oil filler cap.
To change the engine oil
1. Place the ATV on a level surface.
2. Start the engine, warm it up for several min-
1. Engine oil filler cap
2. Dipstick
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1. Maximum level mark
2. Minimum level mark
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utes, and then turn it off.
3. Place an oil pan under the engine to collect
the used oil.
4. Remove the engine oil filler cap, and then re-
move the engine oil drain bolt to drain the oil
from the crankcase.
5. Check the O-ring for damage and replace it if
necessary.
6. Install the engine oil drain bolt, and then tight-
en it to the specified torque.7. Add the specified amount of the recommend-
ed engine oil, and then install and tighten the
engine oil filler cap.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,
do not use oils labeled “ENERGY CONSERV-
ING II” or higher.

Make sure that no foreign material enters the
crankcase.
8. Start the engine, and then let it idle for several
1. Engine oil drain bolt
1

Tightening torque:
Engine oil drain bolt:
20 Nm (2.0 m·kgf, 14.5 ft·lbf)
Recommended oil:
See page 10-1.
Oil quantity:
0.80 L (0.85 US qt) (0.70 Imp.qt)

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minutes while checking it for oil leakage. If oil
is leaking, immediately turn the engine off and
check for the cause.
9. Turn the engine off, and then check the oil lev-
el and correct it if necessary.
EBU23403
Final gear oil
The final gear case must be checked for oil leak-
age before each ride. If any leakage is found, have
a Yamaha dealer check and repair the ATV. In ad-
dition, the final gear oil level must be checked and
the oil changed as follows at the intervals specified
in the periodic maintenance and lubrication chart.
To check the final gear oil level
1. Place the ATV on a level surface.
NOTE:

The final gear oil level must be checked on a cold
engine.
2. Remove the final gear oil filler cap, wipe the
dipstick off with a clean rag, insert it back into
the oil filler hole (without screwing it in), and
then remove it again to check the oil level.
NOTE:

The final gear oil should be between the minimum
and maximum level marks.
3. If the oil is at or below the minimum level mark,
add sufficient oil of the recommended type to
raise it to the correct level.
4. Insert the dipstick into the oil filler hole, and
then tighten the oil filler cap.
1. Final gear oil filler cap
2. Dipstick
3. Maximum level mark
4. Minimum level mark
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2. Remove the air filter case cover by unhooking
the holders.3. Unhook the holder holding the air filter ele-
ment, and then pull out the sponge material
from the air filter element.
4. Wash the sponge material gently but thor-
oughly in solvent.
WARNING

EWB01940
Always use parts cleaning solvent to clean the
sponge material. Never use low-flash-point
solvents or gasoline to clean the sponge mate-
rial because the engine could catch fire or ex-
1. Air filter case cover
2. Air filter case holder
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1. Air filter element holder
2. Sponge material
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