2005 YAMAHA BIG BEAR PRO 400 engine

8-49 1. Air filter element
1.Élément du filtre à air
1. Elemento del filtro de aire
1. Element retaining plate
2. Air filter element 3. Frame
1. Plaque de retenue
2.Élément du filtre à air 3. Armature
1. Placa de retención del elemento
2. Elemento del filtro de aire 3. Bastidor
3. Remove the air filter element.
4. Remove the air filter element from the frame.
5. Wash the air filter element gently but thor-
oughly in solvent.
WARNING
_ Always use parts cleaning solvent to clean the
air filter element. Never use low flash point sol-
vents or gasoline to clean the air filter element
because the engine could catch fire or ex-
plode. _6. Squeeze the excess solvent out of the air fil-
ter element and let it dry.CAUTION:_ Do not twist the air filter element when squeez-
ing it. _7. Inspect the air filter element. If damaged, re-
place it.
8. Apply SAE 10W30 engine oil to the air filter
element.NOTE:_ The air filter element should be wet but not drip-
ping. _
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8-51
9. Apply all-purpose grease to the air filter ele-
ment seat.
10. Install the air filter element on the frame.
11. Install the air filter element.
12. Install the air filter case cover by installing the
screws.
13. Install the seat.NOTE:_ The air filter element should be cleaned every 20–
40 hours. It should be cleaned and lubricated more
often if the machine is operated in extremely dusty
areas. Each time air filter element maintenance is
performed, check the air inlet to the air filter case
for obstructions. 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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8-53
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. _
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8-55
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.
U1C160.book Page 55 Wednesday, May 12, 2004 4:55 PM

8-57 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:
1,450–1,550 r/min
U1C160.book Page 57 Wednesday, May 12, 2004 4:55 PM

8-59 1. Locknut 2. Adjusting nut
1. Contre-écrou 2.Écrou de réglage
1. Contratuerca 2. Tuerca de ajuste
EBU00303
Valve clearance adjustment
The correct valve clearance changes with use, re-
sulting in improper fuel/air supply or engine noise.
To prevent this, the valve clearance must be ad-
justed regularly. This adjustment however, should
be left to a professional Yamaha service techni-
cian.
EBU00305
Select lever safety system cable adjustment
The select lever safety system cable stretches
with use, resulting in improper function.
To prevent this, the cable must be adjusted regu-
larly. This adjustment, however, should be left to a
Yamaha dealer.
U1C160.book Page 59 Wednesday, May 12, 2004 4:55 PM

8-61 1. Adjusting bolt 2. Locknut
a. Throttle lever free play
1. Boulon de réglage 2. Contre-écrou
a. Jeu du levier d’accélération
1. Perno de ajuste 2. Contratuerca
a. Juego libre de la palanca del acelerador
1. Brake pad a. Wear limit
1. Plaquette de frein a. Limite d’usure
1. Pastillas del freno a. Límite de desgaste
EBU00307
Throttle lever adjustmentNOTE:Adjust the engine idling speed before adjusting the
throttle lever free play.1. Loosen the locknut.
2. Turn the adjusting bolt until the throttle lever
free play is 3.0–5.0 mm.
3. Tighten the locknut.
EBU13770
Front brake pad check
Check the brake pads for damage and wear. If a
brake pad thickness is less than 1 mm, have a
Yamaha dealer replace the pads as a set.NOTE:_ The wheels need to be removed to check the
brake pads. (See pages 8-85–8-87 for removal
and installation procedures.) _
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8-83
EBU00570
Cable inspection and lubrication
WARNING
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the outer cov-
ering of control cables becomes damaged.
Cables can also become frayed or kinked. Op-
eration 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.
EBU00727
Brake and shift pedal/brake lever lubrication
Lubricate the pivoting parts of each lever and ped-
al.Recommended lubricant:
Engine oil
Recommended lubricant:
Lithium-soap-based grease
(all-purpose grease)
U1C160.book Page 83 Wednesday, May 12, 2004 4:55 PM