2002 YAMAHA YFM80 engine

8-17
7. Fill the engine with oil and install the dip-
stick.
cC
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: See page 10-2.
Oil quantity:
Periodic oil change:
0.8 L
Total amount:
0.95 L
5NE-9-61 8 4/26/01 1:29 PM Page 16

8-23
EBU00870
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.
5NE-9-61 8 4/26/01 1:29 PM Page 22

8-29
2. Unhook the fastener and remove the air fil-
ter element.
3. Wash the element gently but thoroughly 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.
4. Squeeze the excess solvent out of the filter
and let it dry.
cC
Do not twist the filter element when squeez-
ing it.
5. Inspect the element. If damaged, replace it.
6. Apply SAE10W30 motor oil to the element.
NOTE:
The element should be wet but not dripping.
7. Reinstall the element and front cover.
q
1. Fastener 2. Air filter element1. Attache 2. Elément du filtre à air1. Sujeción 2. Elemento filtrante de aire
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5NE-9-61 8 4/26/01 1:29 PM Page 28

8-31
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 filter element
maintenance is performed, check the air inlet to
the filter case for obstructions. Check the air
cleaner rubber joint to the carburetor and mani-
fold fittings for an air-tight seal. Tighten all fit-
tings securely to avoid the possibility of unfil-
tered air entering the engine.
cC
Never operate the engine with the air filter
element removed. This will allow unfiltered
air to enter, causing rapid engine wear and
possible engine damage. Additionally, opera-
tion without the filter element will affect car-
buretor jetting with subsequent poor perfor-
mance and possible engine overheating.
5NE-9-61 8 4/26/01 1:29 PM Page 30

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.
cC
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.
5NE-9-61 8 4/26/01 1:29 PM Page 32

8-35
EBU00301
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 and set the idle to
the specified idling speed by adjusting the
throttle stop screw. Turn the screw in to
increase engine speed, and out to
decrease engine speed.q
1. Throttle stop screw1. Vis de butée de papillon1. Tornillo tope del acelerador
Specified idle speed:
1,700 ~1,900 r/min
5NE-9-61 8 4/26/01 1:29 PM Page 34

8-37
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.
5NE-9-61 8 4/26/01 1:29 PM Page 36

8-51
EBU00570
Cable inspection and lubrication
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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
5NE-9-61 8 4/26/01 1:29 PM Page 50