engine YAMAHA YFM50R 2006 Service Manual

8-15
Engine oil replacement
1. Place the ATV on a level surface.
2. Warm up the engine for several minutes
and stop it.
3. Place a container under the engine.
4. Remove the dipstick and drain bolt to drain
the oil.
5. Inspect the O-ring and replace if damaged.
6. Install the drain bolt and tighten to specifi-
cation.
1
1. Drain bolt1. Bouchon de vidange1. Perno de drenaje
Tightening torque
Drain bolt:
20 Nm (2.0 m0kgf)
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8-17
7. Fill the engine with oil and install the dip-
stick.
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Be sure no foreign material enters the
crankcase.
8. Warm up the engine for several minutes at
idle speed. Check for oil leakage while
warming up.
cC
If oil leakage is found, stop the engine imme-
diately and check for the cause.
Recommended oil type:
20W50, 20W40, 15W40, 10W40,
10W30, 5W30
Recommended oil classification:
API Service SE, SF, SG type or higher
Oil quantity:
Periodic oil change:
0.8L
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8-23
EBU11820
Spark plug inspection
The spark plug is an important engine compo-
nent and is easy to inspect. The condition of the
spark plug can indicate the condition of the
engine.
For example, a very white center electrode
porcelain color could indicate an intake air leak
or carburetion problem for that cylinder. Do not
attempt to diagnose such problems yourself.
Instead, take the ATV to a Yamaha dealer. You
should periodically remove and inspect the
spark plug because heat and deposits will cause
the spark plug to slowly break down and erode.
If electrode erosion becomes excessive, you
should replace the spark plug with one of the
proper type.
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2
1
1. Fastener 2. Air filter element1. Attache 2. Elément du filtre à air1. Sujeción 2. Elemento filtrante de aire
8-29
2. Remove the air filter case cover by
unhooking the fasteners.
3. Remove the air filter element by unhooking
the fastener.
4. Wash the air filter element gently but thor-
oughly in solvent.
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Always use parts cleaning solvent to clean
the air filter element. Never use low flash
point solvents or gasoline to clean the air fil-
ter element because the engine could catch
fire or explode.
5. Squeeze the excess solvent out of the air
filter element and let it dry.
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Do not twist the air filter element when
squeezing it.
6. Inspect the air filter element. If damaged,
replace it.
7. Apply foam air filter oil to the air filter ele-
ment.
q
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1. Air filter case cover 2. Fastener (×4)1. Couvercle du boîtier de filtre à air 2.Attache (×4)1.Cubierta de la caja del filtro de aire2. Sujeción (×4)
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8-31
NOTE:
The air filter element should be wet but not drip-
ping.
8. Install the air filter element.
9. Install the air filter case cover by hooking
the fasteners onto the air filter case.
10. Install the front cover by installing the bolts.
NOTE:
The air filter element should be cleaned every
20–40 hours. It should be cleaned and lubricat-
ed more often if the machine is operated in
extremely dusty areas. Each time air filter ele-
ment maintenance is performed, check the air
inlet of the air filter case for obstructions. Check
the air cleaner rubber joint to the carburetor and
manifold fittings for an airtight seal. Tighten all
fittings securely to avoid the possibility of unfil-
tered air entering the engine.
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8-33
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Never operate the engine with the air filter
element removed. This will allow unfiltered
air to enter the engine, causing rapid engine
wear and possible engine damage.
Additionally, operation without the filter ele-
ment will affect carburetor jetting with sub-
sequent poor performance and possible
engine overheating.
5YF-9-62 8 2/23/05 6:56 PM Page 8-33

EBU00296
Carburetor adjustment
The carburetor is a vital part of the engine and
requires very sophisticated adjustment. Most
adjusting should be left to a Yamaha dealer who
has the professional knowledge and experience
to do so. However, the idling speed may be per-
formed by the owner as a part of the usual main-
tenance routine.
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The carburetor was set at the Yamaha facto-
ry after many tests. If the settings are dis-
turbed by someone without sufficient techni-
cal knowledge, poor engine performance and
damage may result.
8-35
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8-37
EBU13020
Idle speed adjustment
NOTE:
A diagnostic tachometer must be used for this
procedure.
1. Start the engine and warm it up for a few
minutes at approximately 1,000 to 2,000
r/min. Occasionally rev the engine to 4,000
to 5,000 r/min. The engine is warm when it
quickly responds to the throttle.
2. Connect the tachometer to the spark plug
lead, and then set the idle to the specified
idling speed by adjusting the throttle stop
screw. Turn the screw in direction ato
increase the engine speed, and in direction
bto decrease the engine speed.q
a b
1. Throttle stop screw1. Vis de butée de papillon1. Tornillo tope del acelerador
Specified idle speed:
1,700–1,900 r/min
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8-39
EBU00303
Valve clearance adjustment
The correct valve clearance changes with use,
resulting in improper fuel/air supply or engine
noise. To prevent this, the valve clearance must
be adjusted regularly. This adjustment however,
should be left to a professional Yamaha service
technician.
EBU00304
Cam chain adjustment
The cam chain becomes loose with use, result-
ing in improper valve timing and engine noise.
To prevent this, the cam chain tensioner must
be adjusted regularly. This adjustment should be
left to a Yamaha service technician.
5YF-9-62 8 2/23/05 6:56 PM Page 8-39

8-51
EBU00570
Cable inspection and lubrication
w
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the outer
covering of control cables becomes dam-
aged. Cables can also become frayed or
kinked. Operation of controls could be
restricted, which could cause an accident or
injury.
Lubricate the inner cables and the cable ends. If
the cables do not operate smoothly, ask a
Yamaha dealer to replace them.
Recommended lubricant:
Engine oil
5YF-9-62 8 2/23/05 6:56 PM Page 8-51