engine YAMAHA BRUIN 250 2005 Service Manual

8-21 1. Footboard 2. Bolt (× 8)
1. Repose-pied 2. Boulon (× 8)
1. Plataforma para los pies 2. Perno (× 8)
1. Adjusting nut (brake rod)
1.Écrou de réglage (tringle de frein)
1. Tuerca de ajuste (barra del freno)
CAUTION:_ When removing the engine oil drain bolt, the
compression spring, oil strainer and O-ring
will fall out. Take care not to lose these parts. _NOTE:_ Skip steps 5–11 if the oil filter element is not being
cleaned. _5. Remove the footboard by removing the bolts.
6. Fully loosen the brake pedal free play adjust-
ing nut, push the brake pedal downward, and
then remove the oil filter element cover bolts.
U1P060.book Page 21 Monday, August 2, 2004 12:19 PM

8-23 1. Oil filter element cover 2. Adjusting nut
1. Couvercle de l’élément du filtre à huile 2.Écrou de réglage
1. Cubierta del elemento del filtro de aceite
2. Tuerca de ajuste
1. Engine oil filter element 2. O-ring
1.Élément du filtre à huile de moteur 2. Joint torique
1. Elemento del filtro de aceite de motor
2. Junta tórica
7. Remove the oil filter element cover and oil fil-
ter element.NOTE:_ To remove or install the oil filter element cover and
oil filter element, move the select lever safety sys-
tem cable away from the cover. _CAUTION:_ Do not loosen the adjusting nuts shown when
removing the oil filter element cover or oil filter
element. _8. Clean the oil strainer and oil filter element
with solvent.
9. Check the O-ring for damage and replace it if
necessary.NOTE:_ Make sure the O-ring is seated properly. _
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8-25
10. Install the oil filter element.
11. Install the oil filter element cover by installing
the bolts, and then tightening them to the
specified torque.
12. Install the oil strainer, compression spring,
O-ring and engine oil drain bolt, and then
tighten the engine oil drain bolt to the speci-
fied torque.CAUTION:_ Before installing the engine oil drain bolt, be
sure to install the O-ring, compression spring
and oil strainer. _
Tightening torque:
Oil filter element cover bolt:
10 Nm (1.0 m·kgf)
Tightening torque:
Engine oil drain bolt:
43 Nm (4.3 m·kgf)
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8-27
13. Add the specified amount of the recommend-
ed engine oil, then install and tighten the en-
gine oil filler cap.CAUTION:_

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
CONSERVING II” or higher.


Make sure that no foreign material enters
the crankcase.
_
Recommended engine oil:
See page 10-2.
Oil quantity:
Without oil filter element removal:
1.50 L
With oil filter element removal:
1.60 L
U1P060.book Page 27 Monday, August 2, 2004 12:19 PM

8-29 1. Bolt A (× 6) 2. Bolt B (× 2)
1. Boulon A (× 6) 2. Boulon B (× 2)
1. Perno A (× 6) 2. Perno B (× 2)
14. Start the engine, and then let it idle for seve-
ral minutes while checking it for oil leakage. If
oil is leaking, immediately turn the engine off
and check for the cause.
15. Turn the engine off, and then check the oil
level and correct it if necessary.
16. Install the footboard by installing the bolts,
and then tightening them to the specified
torque.
17. Adjust the brake pedal free play. (See page
8-67.) Tightening torque:
Footboard bolt A:
3.8 Nm (0.38 m·kgf)
Footboard bolt B:
6.5 Nm (0.65 m·kgf)
U1P060.book Page 29 Monday, August 2, 2004 12:19 PM

8-37 1. Spark plug cap
1. Capuchon de bougie
1. Tapa de bujía
1. Spark plug wrench
1. Clé à bougie
1. Llave de bujía
EBU14550
Spark plug inspection
Removal
1. Remove the spark plug cap.
2. Use the spark plug wrench in the owner’s tool
kit to remove the spark plug as shown.
Inspection
The spark plug is an important engine component
and is easy to inspect. The condition of the spark
plug can indicate the condition of the engine.
The ideal color on the white insulator around the
center electrode is a medium-to-light tan color for
an ATV that is being ridden normally.
Do not attempt to diagnose such problems your-
self.
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 elec-
trode erosion becomes excessive, or if carbon and
other deposits are excessive, you should replace
the spark plug with the specified plug.
U1P060.book Page 37 Monday, August 2, 2004 12:19 PM

8-45 1. Air filter element
1.Élément du filtre à air
1. Elemento del filtro de aire
1. Air filter element 2. Foam cover
1.Élément du filtre à air 2. Cache en mousse
1. Elemento del filtro de aire 2. Forro de espuma
3. Pull the air filter element out.
4. Remove the foam cover from the air filter ele-
ment.
5. Wash the foam cover gently but thoroughly in
water or solvent.
WARNING
_ When using solvent to clean the foam cover,
always use parts cleaning solvent. Never use
low flash point solvents or gasoline to clean
the foam cover because the engine could
catch fire or explode. _6. Squeeze the excess solvent out of the foam
cover and let it dry.CAUTION:_

Do not twist the foam cover when squeez-
ing it.


Do not apply oil to the foam cover.
_
U1P060.book Page 45 Monday, August 2, 2004 12:19 PM

8-47
7. Tap the air filter element lightly to remove
most of the dust and dirt. Blow out the re-
maining dirt with compressed air as shown. If
the air filter element is damaged, replace it.NOTE:_ Check the foam cover for damage and replace it if
necessary. _8. Install the foam cover onto the air filter ele-
ment.
9. Install the air filter element.
10. Install the air filter case cover by fastening the
holders.
11. Install the seat.NOTE:_ The air filter element should be cleaned every 20–
40 hours. It should be cleaned more often if the
ATV is operated in extremely dusty areas. Each
time air filter element maintenance is performed,
check the air inlet to the air filter case for obstruc-
tions. Check the air filter element rubber joint to the
carburetor and manifold fittings for an airtight seal.
Tighten all fittings securely to avoid the possibility
of unfiltered air entering the engine. _
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8-49
CAUTION:_ Never operate the engine with the air filter ele-
ment removed. This will allow unfiltered air to
enter, causing rapid engine wear and possible
engine damage. Additionally, operation with-
out the air filter element will affect carburetor
jetting with subsequent poor performance and
possible engine overheating. _
EBU00296
Carburetor adjustment
The carburetor is a vital part of the engine and re-
quires very sophisticated adjustment. Most adjust-
ing should be left to a Yamaha dealer who has the
professional knowledge and experience to do so.
However, the idling speed may be performed by
the owner as a part of the usual maintenance rou-
tine.CAUTION:
The carburetor was set at the Yamaha factory
after many tests. If the settings are disturbed
by someone without sufficient technical
knowledge, poor engine performance and
damage may result.
U1P060.book Page 49 Monday, August 2, 2004 12:19 PM

8-51 1. Throttle stop screw
1. Vis d’arrêt de l’accélérateur
1. Tornillo de tope del acelerador
EBU13020
Idle speed adjustmentNOTE:_ A diagnostic tachometer must be used for this pro-
cedure. _1. Start the engine and warm it up for a few min-
utes 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
a to in-
crease the engine speed, and in direction
b
to decrease the engine speed.
Specified idle speed:
1,400–1,500 r/min
U1P060.book Page 51 Monday, August 2, 2004 12:19 PM