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EBU28320
Checking the spark plugs
The spark plugs are important engine compo-
nents, which are easy to check. Since heat and de-
posits will cause any spark plug to slowly erode,
the spark plugs should be removed and checked in
accordance with the periodic maintenance and lu-
brication chart. In addition, the condition of the
spark plugs can reveal the condition of the engine.
To remove a spark plug
1. Remove the spark plug cap.
2. Remove the spark plug as shown, with the
spark plug wrench included in the owner’s toolkit.
To check the spark plugs
1. Check that the porcelain insulator around the
center electrode of each spark plug is a medi-
um-to-light tan (the ideal color when the ATV
is ridden normally).
2. Check that all spark plugs installed in the en-
gine have the same color.NOTE:
If any spark plug shows a distinctly different color,
the engine could be operating improperly. Do not
attempt to diagnose such problems yourself. In-
1. Spark plug cap
1
1. Spark plug wrench
1
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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.4. Make sure the gasket is properly positioned,
then insert the tailpipe into the muffler and
align the screw holes.
5. Install the screws and tighten them.
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
1. Screw
1
1. Tailpipe
2. Spark arrester
3. Gasket
1
2
3
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tion chart.
NOTE:
A diagnostic tachometer is needed to make this
adjustment.
The carburetor synchronization and the throttle
cable free play must be checked, and adjusted if
necessary, before adjusting the engine idling
speed.
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. Turn in both pilot air screws until they lightly
seat.
4. Turn out both pilot air screws to specification.
(See the “Changing the carburetor settings”
section on the page 8-21.)5. Remove the seat. (See page 4-11.)
6. Check the engine idling speed and, if neces-
sary, adjust it to specification by turning the
throttle stop screws at the carburetors. To in-
crease the engine idling speed, turn the throt-
tle stop screws in direction (a), and to
decrease it, turn the screws in direction (b).
1. Pilot air screw
1
Page 113 of 140

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WARNING
EWB02090
Operating with improperly serviced or adjust-
ed brakes could cause the brakes to malfunc-
tion, resulting in reduced braking
performance. This could increase the chance
of a collision or accident. After adjusting the
parking brake free play, block the rear of the
ATV off the ground and spin the rear wheels.
Check to make sure there is no brake drag. If
brake drag is noticed, perform the adjustment
again.
EBU24740
Brake light switches
The operation of the brake light switches must be
checked and, if necessary, adjusted at the inter-
vals specified in the periodic maintenance and lu-
brication chart.
The brake light switch for the brake pedal can be
adjusted as follows, but the other brake light
switches should be adjusted by a Yamaha dealer.
NOTE:
The brake light switch is properly adjusted when
the brake light comes on just before braking takes
effect.
Turn the adjusting nut while holding the brake light
switch in place. To make the brake light come on
earlier, turn the adjusting nut in direction (a). To
make the brake light come on later, turn the adjust-
ing nut in direction (b).
EBU24810
Adjusting the clutch lever free play
The clutch lever free play must be checked and, if
necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
The clutch lever free play should measure as
1. Brake light switch
2. Brake light switch adjusting nut
1
2
(a)
(b)
Page 120 of 140
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Right side
EBU26881
Replacing a headlight bulb
If a headlight bulb burns out, replace it as follows.
1. Remove the headlight unit by removing the
screw.2. Remove the headlight bulb holder cover.
1. Grease nipple
1
1. Screw
1
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3. Remove the bulb holder by turning it counter-
clockwise.4. Remove the defective bulb.
WARNING
EWB02200
A headlight bulb is hot when it is on and imme-
diately after it is turned off. Wait for the bulb to
cool before touching or removing it. You can
be burned, or a fire could start if the bulb
touches something flammable.
5. Place a new bulb into position, and then install
the bulb holder by turning it clockwise.
1. Headlight bulb holder cover
1
1. Headlight bulb holder
1
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CAUTION:
ECB00650
Do not touch the glass part of the headlight
bulb to keep it free from oil, otherwise the
transparency of the glass, the luminosity of the
bulb, and the bulb life will be adversely affect-
ed. Thoroughly clean off any dirt and finger-
prints on the headlight bulb using a cloth
moistened with alcohol or thinner.
6. Install the bulb holder cover.CAUTION:
ECB00680
Make sure the bulb holder cover is securely fit-
ted over the bulb holder and seated against the
reflector.
7. Place the headlight unit in the original posi-
tion, and then install the screw.
8. Adjust the headlight beam if necessary.
1. Do not touch the glass part of the bulb.
1
1. Headlight bulb holder cover
2. Headlight bulb holder
3. Headlight unit
1
2
3
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EBU25550
Adjusting a headlight beam
CAUTION:
ECB00690
It is advisable to have a Yamaha dealer make
this adjustment.
To raise a headlight beam, turn the adjusting
screw in direction (a).
To lower a headlight beam, turn the adjusting
screw in direction (b).
EBU25610
Replacing the tail/brake light bulb
If the tail/brake light bulb burns out, replace it asfollows.
1. Remove the bulb holder (together with the
bulb) by turning it counterclockwise.
2. Remove the defective bulb by pushing it in
and turning it counterclockwise.
1. Headlight beam adjusting screw
1
(a) (b)
1. Tail/brake light bulb holder
1