2009 YAMAHA YFM90R engine

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To check the spark plug1. 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).TIPIf 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.
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.1. Spark plug wrench
Specified spark plug:NGK/CR7HSA
Spark plug gap: 0.6–0.7 mm (0.024–0.028 in)1. Spark plug gap
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2. Clean the surface of the spark plug gasketand 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.TIPIf 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 assoon as possible.
4. Install the spark plug cap. 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. To check the engine oil level
1. Place the ATV on a level surface.
2. Check the engine oil level on a cold engine.
TIPIf 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-1. Engine oil filler cap
2. Dipstick
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tles for an accurate reading.
3. Remove the engine oil filler cap, and then wipe the dipstick off with a clean rag.
Tightening torque:
Spark plug:12.0 Nm (1.20 m·kgf, 8.9 ft·lbf)
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4. Insert the dipstick into the filler hole (withoutscrewing it in), and then remove it again to
check the oil level.TIPThe engine oil should be between the minimumand 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. Maximum level mark
2. Minimum level mark
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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 remove the engine oil drain bolt to drain the
oil from the crankcase.
5. Check the washer for damage and replace it if necessary.
6. Install the engine oil drain bolt, and then tighten it to the specified torque.
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2
3
4
1. Engine oil drain bolt
2. O-ring
3. Spring
4. Oil filter element

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7. Add the specified amount of the recommend-ed engine oil, and then install and tighten the
engine oil filler cap.
Tightening torque:
Engine oil drain bolt:8 Nm (0.8m·kgf, 5.8 ft·lbf)
Recommended oil: See page 10-1.
Oil quantity: 0.8 L (0.84 US qt) (0.70 Imp.qt)N O T I C EDo not mix any chemical additives. Do
not use oils with a diesel specification
of "CD" or oils of a higher quality than
sp eci fi ed . I n ad d i ti o n , d o n o t u se o i ls l ab el e d " E N E R G Y C O N S E R V I N G I I " o r
higher.the crankcase.
8. Start the engine, and then let it idle for severalMake sure that no foreign material enters 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.

N O T I C EDo not twist the sponge material when squeez-ing it.5. Check the sponge material and replace it if damaged.
1. Air filter element holder
2. Sponge material
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2
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2. Remove the air filter element by removing the
3. Wash the sponge material gently but thor- oughly in solvent. 4. Squeeze the excess solvent out of the sponge
material and let it dry.
screw, and then pull off the sponge material
from the air filter element holder.
WARNING
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-
plode.

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6. Apply Yamaha foam air filter oil or other qual-ity foam air filter oil to the sponge material.TIPThe sponge material should be wet but not drip-ping.
7. Install the sponge material onto the air filter element holder.
8. Place the air filter element in the original position, and then install the screw.
9. Install the air filter case cover by installing the bolts.TIPThe 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 casefor obstructions.N O T I C E 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
poor performance and possible engine over-
heating.
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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.N O T I C E 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 ordamage to the engine. Adjusting the engine idling speed The engine idling speed must be checked and, if
necessary, adjusted as follows at the intervals
specified in the periodic maintenance and lubrica-
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WARNING
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 totouching exhaust components.

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tion chart.TIPA diagnostic tachometer is needed to make thisadjustment.1. Start the engine and warm it up.TIPThe engine is warm when it quickly responds to thethrottle.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).
TIPIf the specified idling speed cannot be obtained as
described above, have a Yamaha dealer make theadjustment. 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.1. Throttle stop screwEngine idling speed:1600–1800 r/min
1
(b)
(a)