engine YAMAHA YFM250R 2008 Owner's Guide

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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.
EBU28881
Engine oil and oil filter element
The engine oil level should be checked before
each ride. In addition, the oil must be changed and
the oil filter element cleaned at the intervals speci-
fied in the periodic maintenance and lubrication
chart. Specified spark plug:
NGK/DR7EA
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
1. Spark plug cap
Tightening torque:
Spark plug:
18 Nm (1.8 m·kgf, 13 ft·lbf)

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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 (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.
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
3. Maximum level mark
4. Minimum level mark
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To change the engine oil (with or without oil
filter element cleaning)
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.
CAUTION:

ECB00310
When removing the engine oil drain bolt, thecompression spring, oil strainer and O-ring will
fall out. Take care not to lose these parts.
NOTE:

Skip steps 5–9 if the oil filter element is not being
cleaned.
5. Remove the oil filter element cover by remov-
ing the bolts, and then remove the oil filter el-
ement.
6. Clean the oil filter element with solvent.
7. Check the O-rings for damage and replace it if
necessary.
1. Engine oil drain bolt
1

1. Oil filter element cover
2. Bolt
1 2

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8. Install the oil filter element and O-ring.
NOTE:

Make sure that the O-ring is properly seated.
9. Install the oil filter element cover by installing
the bolts, and then tighten them to the speci-
fied torque.10. Install the engine oil drain bolt and tighten it to
the specified torque.CAUTION:
ECB00320
Before installing the engine oil drain bolt, be
sure to install the O-ring, compression spring
and oil strainer.
11. Add the specified amount of the recommend-
ed engine oil, and then install and tighten the
engine oil filler cap.
NOTE:

Be sure to wipe off spilled oil on any parts after the
1. Oil filter element
2. O-ring
Tightening torque:
Oil filter element cover bolt:
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
1
2
2

Tightening torque:
Engine oil drain bolt:
20 Nm (2.0 m·kgf, 14.5 ft·lbf)
Recommended oil:
See page 10-1.
Oil quantity:
Without oil filter element replacement:
1.25 L (1.32 US qt) (1.10 Imp.qt)
With oil filter element replacement:
1.35 L (1.43 US qt) (1.19 Imp.qt)

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engine and exhaust system have cooled down.
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.
12. Start the engine, and then let it idle for several
minutes while checking it for oil leakage. If oil
is leaking, immediately turn the engine off and
check for the cause.
13. Turn the engine off, wait at least ten minutes,
and then check the oil level and correct it if
necessary.
EBU23702
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 dustyareas.
NOTE:

There is a check hose at the bottom of the air filter
case. If dust or water collects in this hose, empty
the hose and clean the air filter element and air fil-
ter case.
1. Remove the seat. (See page 4-10.)
2. Remove the air filter case cover by unhooking
the holders.
1. Air filter case check hose
1

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7. 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-
plode.
8. 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.
9. Check the sponge material and replace it if
damaged.
10. Apply a quality foam air filter oil to the sponge
material.
NOTE:

The sponge material should be wet but not drip-
ping.
11. Pull the sponge material over the air filter ele-
ment frame.
1. Sponge material
2. Air filter element frame
1
2

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12. Install the washer onto the air filter element
frame, and then insert the wing bolt into the
hole in the air filter element frame.
CAUTION:

ECB00451
Be sure to install the washer with the bent edge
facing outward as shown.
13. Insert the air filter element into the air filter
case, and then tighten the wing bolt.
14. Install the air filter case cover by hooking the
holders onto the air filter case.
15. Install the seat.
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. Check the air filter case rubber
joint to the carburetor fittings and the rubber joint
manifold fittings for an air-tight seal. Tighten all fit-
tings securely to avoid the possibility of unfiltered
air entering the engine.
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
poor performance and possible engine over-
heating.
1. Washer
1

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5. Install the bolts and tighten them to the speci-
fied torque.
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
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.
1. Gasket
2. Tailpipe
3. Bolt
Tightening torque:
Tailpipe bolt:
11 Nm (1.1 m·kgf, 8.0 ft·lbf)
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EBU24000
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-
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).
NOTE:

If the specified idling speed cannot be obtained as
described above, have a Yamaha dealer make the
adjustment.
EBU24043
Adjusting the throttle cable free play
The throttle cable free play should be checked
and, if necessary, adjusted at the intervals speci-
fied in the periodic maintenance and lubrication
1. Throttle stop screw
Engine idling speed:
1500–1600 r/min
1
(a)
(b)

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chart.
The throttle cable free play should measure 2.0–
4.0 mm (0.08–0.16 in) at the throttle lever. Period-
ically check the throttle cable free play and, if nec-
essary, adjust it as follows.
NOTE:

The engine idling speed must be checked, and ad-
justed if necessary, before adjusting the throttle ca-
ble free play.
1. Loosen the locknut.
2. To increase the throttle cable free play, turn
the adjusting bolt in direction (a). To decrease
the throttle cable free play, turn the adjusting
bolt in direction (b).
3. Tighten the locknut.
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. Locknut
2. Throttle cable free play adjusting bolt
3. Throttle lever free play
3 2
1
(a)(b)