engine YAMAHA YFM350R-W 2012 Service Manual

8-17
8
6. Wash the sponge material gently but thor-
oughly in solvent. WARNING! Always use
parts cleaning solvent to clean the sponge
material. Never use low-flash-point sol-
vents or gasoline to clean the sponge ma-
terial because the engine could catch fire
or explode.
[EWB01941]
7. Squeeze the excess solvent out of the sponge
material and let it dry. NOTICE: Do not twist
the sponge material when squeezing it.
[ECB00441]
8. Check the sponge material and replace it if
damaged.
9. 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.10. Pull the sponge material over the air filter ele-
ment frame.
11. Apply all-purpose grease to the air filter ele-
ment seat.
12. Insert the air filter element into the air filter
case, and then install the air filter case cover
by hooking the holders onto the air filter case.
1. Air filter element retaining plate
2. Air filter element frame
3. Sponge material
4. Air filter element seatU10P70E0.book Page 17 Thursday, July 21, 2011 8:51 AM

8-18
8 NOTICE: Make sure that the air filter ele-
ment is properly seated in the air filter
case. Never operate the engine with the air
filter element removed. This will allow un-
filtered air to enter the engine, causing rap-
id engine wear and possible engine
damage. Additionally, operation without
the air filter element will affect carburetor
jetting with subsequent poor performance
and possible engine overheating.
[ECB00461]
13. Install the seat.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 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.
EBU27703Cleaning the spark arrester Select a well-ventilated area free of combustible
materials and make sure the exhaust and muffler
are cool.
1. Remove the tailpipe bolt.
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 inside
of the tailpipe housing.1. Tailpipe bolt
2. Tailpipe
1
2
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8-19
84. Insert the tailpipe into the muffler and align the
bolt holes.
5. Install the bolt and tighten it to the specified
torque.
6. Remove the purging bolt and the gasket.7. Start the engine and rev it up approximately
twenty times while momentarily creating ex-
haust system back pressure by blocking the
end of the muffler with a shop towel.
8. Stop the engine and allow the exhaust pipe to
cool.
9. Check the gasket for damage, and replace it if
necessary.
10. Install the gasket and the purging bolt, and
then tighten the bolt to the specified torque.
1. Tailpipe
2. Spark arresterTightening torque:
Tailpipe bolt:
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
1. Purging bolt
2. Gasket
12
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8-20
8
WARNING
EWB02380Never run the engine in an enclosed area when
purging the spark arrester, otherwise it could
cause injury to the eyes, burns, carbon monox-
ide poisoning, possibly leading to death, and
start a fire.
Always let the exhaust system cool prior to
touching exhaust components.
Always wear eye protection, and make sure
no one is behind the ATV.
Make sure there are no combustible materi-
als in the area.EBU23940Adjusting 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 aYamaha 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.
NOTICEECB00480The 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.EBU24000Adjusting 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.TIPA diagnostic tachometer is needed to make this
adjustment.1. Start the engine and warm it up. Tightening torque:
Purging bolt:
27 Nm (2.7 m·kgf, 20 ft·lbf)
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8-21
8
TIPThe 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).
TIPIf the specified idling speed cannot be obtained as
described above, have a Yamaha dealer make the
adjustment.EBU24047Adjusting the throttle lever free play The throttle lever free play should be checked and,
if necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
The throttle lever free play should measure 2.0–
4.0 mm (0.08–0.16 in) as shown. Periodically
check the throttle lever free play and, if necessary,
adjust it as follows.TIPThe engine idling speed must be checked, and ad-
justed if necessary, before adjusting the throttle le-
ver free play.1. Slide the rubber cover back.
2. Loosen the locknut.
3. To increase the throttle lever free play, turn
the throttle lever free play adjusting bolt in di-
rection (a). To decrease the throttle lever free
play, turn the adjusting bolt in direction (b).
1. Throttle stop screwEngine idling speed:
1450–1550 r/min
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8-22
8 4. Tighten the locknut.
5. Slide the rubber cover to its original position.
EBU24060Valve 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.
EBU29601Brakes Replacement of brake components requires pro-
fessional knowledge. Brake service should be per-
formed by a Yamaha dealer.
WARNING
EWB02571Operating with improperly serviced or adjust-
ed brakes could lead to a loss in braking ability
and an accident.EBU24130Checking the front and rear brake pads The front and rear brake pads must be checked for
wear at the intervals specified in the periodic main-
tenance and lubrication chart.EBU28791Front brake pads
Each brake pad is provided with wear indicator
grooves, which allow you to check the brake pad
wear without having to disassemble the brake. To
check the brake pad wear, check the wear indica-
tor grooves. If a brake pad has worn to the point
that a wear indicator groove almost appears, have
a Yamaha dealer replace the brake pads as a set.
1. Rubber cover
2. Throttle lever free play adjusting bolt
3. Locknut
4. Throttle lever free play
3
12
4
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8-30
8
3. If the drive chain slack is incorrect, adjust it as
follows.
To adjust the drive chain slack
1. Place the ATV on a level surface.
2. Loosen the axle holding nuts.3. Loosen the locknut on each side of the swing-
arm. To tighten the drive chain, turn the ad-
justing bolts in direction (a). To loosen the
drive chain, turn the adjusting bolts in direction
(b) and push the wheels forward. Turn each
adjusting bolt exactly the same amount to
maintain correct axle alignment. NOTICE: Im-
proper drive chain slack will overload the
engine as well as other vital parts of the
ATV and can lead to drive chain slippage
or breakage. To prevent this from occur-
ring, keep the drive chain slack within the
specified limits.
[ECB00542]
Drive chain slack:
25.0–35.0 mm (0.98–1.38 in)1. Drive chain slack
1. Axle holding bolt (upper)
2. Axle holding bolt (lower)
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8
EBU24882Lubricating the drive chain The drive chain must be cleaned and lubricated at
the intervals specified in the periodic maintenance
and lubrication chart, otherwise it will quickly wear
out, especially when riding in dusty or wet areas.
Service the drive chain as follows.NOTICEECB00561The drive chain must be lubricated after wash-
ing the ATV or riding in the rain or wet areas.1. Clean the drive chain with kerosene and a
small soft brush. NOTICE: To prevent dam-
aging the O-rings, do not clean the drive
chain with steam cleaners, high-pressure
washers or inappropriate solvents.
[ECB00571]
2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a
special O-ring chain lubricant. NOTICE: Do
not use engine oil or any other lubricants
for the drive chain, as they may contain
substances that could damage the O-
rings.
[ECB00581]
EBU24902
Checking and lubricating the cables The operation and the condition of all control ca-
bles should be checked before each ride, and the
cables and cable ends should be lubricated if nec- Tightening torques:
Locknut:
16 Nm (1.6 m·kgf, 12 ft·lbf)
Axle holding nut (upper):
120 Nm (12 m·kgf, 87 ft·lbf)
Axle holding nut (lower):
73 Nm (7.3 m·kgf, 53 ft·lbf)1. O-ring
1 1
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8-33
8essary. If a cable is damaged or does not move
smoothly, have a Yamaha dealer check or replace
it.
WARNING
EWB02581
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the cable
sheaths become damaged, and cables can
also become frayed or kinked, which could
restrict the operation of controls and lead to
an accident or injury.
Always make sure all control cables work
smoothly before you begin riding in cold
weather. If the control cables are frozen or do
not work smoothly, you could be unable to
control the ATV, which could lead to an acci-
dent or collision.
EBU24922Checking and lubricating the brake and
clutch levers The operation of the brake and clutch levers
should be checked before each ride, and the lever
pivots should be lubricated if necessary.
Brake lever Recommended lubricant:
Yamaha Chain and Cable Lube or engine oilRecommended lubricants:
Brake lever:
Silicone grease
Clutch lever:
Lithium-soap-based grease
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8-46
8
EBU25752Troubleshooting chart
Check the fuel level in
the fuel tank.1. Fuel
There is enough fuel.
There is no fuel.
Check the compression.
Supply fuel.
The engine does not start.
Check the compression.
Operate the electric starter.2. Compression
There is compression.
There is no compression.
Check the ignition.
Have a Yamaha dealer
check the ATV.
Remove the spark plug
and check the electrodes.3. Ignition
Wipe off with a dry cloth and correct the
spark plug gap, or replace the spark plug.
Have a Yamaha dealer check the ATV.
The engine does not start.
Have a Yamaha dealer
check the ATV.
The engine does not start.
Check the battery.
Operate the electric starter.4. Battery
The engine turns over
quickly.
The engine turns over
slowly.
The battery is good.Check the battery lead connections,
and have a Yamaha dealer charge
the battery if necessary.
DryWet
Open the throttle halfway and operate
the electric starter.
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