YAMAHA YFM50R 2008 Manual Online

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To check the engine oil level
1. Place the ATV on a level surface.
2. Check the engine oil level on a cold engine.
NOTE:

If the engine was started before checking the oil
level, be sure to warm up the engine sufficiently,
and then wait at least ten minutes until the oil set-
tles for an accurate reading.
3. Remove the engine oil filler cap, and then
wipe the dipstick off with a clean rag.
4. Insert the dipstick into the filler hole (withoutscrewing 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.
5. 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.
6. Insert the dipstick into the oil filler hole, and
then tighten the engine oil filler cap.
1. Engine oil filler cap
2. Dipstick
12

1. Maximum level mark
2. Minimum level mark
1
2

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To change the engine oil
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. 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, wait at least ten minutes,
and then check the oil level 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
2 3
4
1

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To change the final gear oil
1. Place the ATV on a level surface.
2. Place an oil pan under the final gear case to
collect the used oil.
3. Remove the final gear oil filler cap and the fi-
nal gear oil drain bolt to drain the oil from the
final gear case.
4. Install the drain bolt, and then tighten it to the
specified torque.5. Add the specified amount of the recommend-
ed final gear oil, and then check the oil level.CAUTION:
ECB00420
Be sure no foreign material enters the final
gear case.
6. Install and tighten the oil filler cap.
7. Check the final gear case for oil leakage. If oil
is leaking, check for the cause.
EBU23803
Cleaning the air filter element
The air filter element should be cleaned at the in-
tervals specified in the periodic maintenance and
lubrication chart. Clean the air filter element more
frequently if you are riding in unusually wet or dusty
areas.
NOTE:

There is a check hose at the bottom of the air filter
case. If dust or water collects in this hose, empty
1. Final gear oil drain bolt
Tightening torque:
Final gear oil drain bolt:
23 Nm (2.3 m·kgf, 16.6 ft·lbf)
1

Recommended final gear oil:
See page 10-1.
Oil quantity:
0.12 L (0.13 US qt) (0.11 Imp.qt)

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the hose and clean the air filter element and air fil-
ter case.
1. Remove the panel shown by removing the
bolts.
1. Air filter case check hose
1

1. Panel
2. Bolt
122

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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
2
2
1

1. Air filter element holder
2. Sponge material
1
2

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plode.
5. Squeeze the excess solvent out of the sponge
material and let it dry.
CAUTION:

ECB00440
Do not twist the sponge material when squeez-
ing it.
6. Check the sponge material and replace it if
damaged.
7. Apply a quality foam air filter oil to the sponge
material.
NOTE:

The sponge material should be wet but not drip-
ping.
8. Install the sponge material into the air filter el-
ement.
9. Place the air filter element in the original posi-
tion, and then hook the holder.
10. Install the air filter case cover by hooking the
holders onto the air filter case.
11. Install the panel by installing the bolts.
NOTE:

The air filter element should be cleaned every 20–
40 hours. It should be cleaned and lubricated more
often if the ATV is operated in extremely dusty ar-
eas. Each time the air filter element maintenance
is performed, check the air inlet of the air filter case
for obstructions.
CAUTION:

ECB00460

Make sure that the air filter element is prop-
erly seated in the air filter case.

Never operate the engine with the air filter el-
ement removed. This will allow unfiltered air
to enter the engine, causing rapid engine
wear and possible engine damage. Addition-
ally, operation without the air filter element
will affect carburetor jetting with subsequent

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poor performance and possible engine over-
heating.
EBU27630
Cleaning the spark arrester
Be sure the exhaust pipe and muffler are cool be-
fore cleaning the spark arrester.
1. Remove the screws.
2. Remove the tailpipe by pulling it out of the
muffler.
3. Tap the tailpipe lightly, and then use a wire
brush to remove any carbon deposits from the
spark arrester portion of the tailpipe and insideof the tailpipe housing.
4. Insert the tailpipe into the muffler and align the
screw holes.
5. Install the screws and tighten them.WARNING
EWB02340
Do not start the engine when cleaning the
spark arrester, otherwise it could cause injury
to the eyes, burns, carbon monoxide poison-
ing, possibly leading to death, and start a fire.
Always let the exhaust system cool prior to
1. Screw
1

1. Tailpipe
2. Spark arrester
3. Screw
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touching exhaust components.
EBU23940
Adjusting the carburetor
The carburetor should be checked and, if neces-
sary, adjusted at the intervals specified in the peri-
odic maintenance and lubrication chart. The
carburetor is an important part of the engine and
requires very sophisticated adjustment. Therefore,
most carburetor adjustments should be left to a
Yamaha dealer, who has the necessary profes-
sional knowledge and experience. The adjustment
described in the following section, however, may
be performed by the owner as part of routine main-
tenance.
CAUTION:

ECB00480
The carburetor has been set and extensively
tested at the Yamaha factory. Changing these
settings without sufficient technical knowl-
edge may result in poor performance of or
damage to the engine.
EBU24000
Adjusting the engine idling speed
The engine idling speed must be checked and, ifnecessary, adjusted as follows at the intervals
specified in the periodic maintenance and lubrica-
tion chart.
NOTE:

A diagnostic tachometer is needed to make this
adjustment.
1. Start the engine and warm it up.
NOTE:

The engine is warm when it quickly responds to the
throttle.
2. Attach the tachometer to the spark plug lead.
3. Check the engine idling speed and, if neces-
sary, adjust it to specification by turning the
throttle stop screw at the carburetor. To in-
crease the engine idling speed, turn the throt-
tle stop screw in direction (a), and to decrease
it, turn the screw in direction (b).

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NOTE:

If the specified idling speed cannot be obtained as
described above, have a Yamaha dealer make the
adjustment.
EBU27071
Checking the throttle cable free play
The throttle cable free play should be checked at
the intervals specified in the periodic maintenance
and lubrication chart.The throttle cable free play should measure 1.0–
3.0 mm (0.04–0.12 in) at the throttle lever. Period-
ically check the throttle cable free play and, if nec-
essary, have a Yamaha dealer adjust it.
EBU24060
Valve 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.
1. Throttle stop screw
Engine idling speed:
1750–1850 r/min
1 (a) (b)

1. Throttle lever free play
1