2004 YAMAHA BIG BEAR PRO 400 engine

8-47
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. _
U4SH6B.book Page 47 Tuesday, May 27, 2003 4:39 PM

8-49
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.
U4SH6B.book Page 49 Tuesday, May 27, 2003 4:39 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:
1,350–1,450 r/min
U4SH6B.book Page 51 Tuesday, May 27, 2003 4:39 PM

8-53 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.
U4SH6B.book Page 53 Tuesday, May 27, 2003 4:39 PM

8-55 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 page 8-79 for removal and in-
stallation procedures.) _
U4SH6B.book Page 55 Tuesday, May 27, 2003 4:39 PM

8-77
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)
U4SH6B.book Page 77 Tuesday, May 27, 2003 4:39 PM

8-99
EBU00440Troubleshooting chart1. Fuel
Check if there is fuel
in the fuel tank.There is fuel.Turn the fuel cock
lever to “OFF”.No fuel.Fuel cock is
clogged.
Clean the
fuel cock. Some fuel.Turn the fuel cock
lever to “RES”.Restart the engine.
No fuel.Supply fuel.
2. Compression
Use the electric
starter to see if
there is compression.There is compression.
Compression normal.
No compression.Ask a Yamaha dealer to
inspect.
3. Ignition
Remove the
spark plug and
check electrodes.WetWipe clean with dry cloth.
DryAttach spark plug cap and
ground to chassis.Use the
electric starter.Spark is good.Ignition system is
normal.
Spark is weak.
Adjust the spark plug gap
or replace the spark plug. No spark.
Ask a Yamaha dealer to
inspect. 4. Battery
Use the electric starter.Engine turns over
quickly.Battery is good.
Engine turns over
slowly.Check the connections.Check the
fuel flow.
Turn the fuel cock
lever to “ON”.
Remove the fuel hose
from the fuel cock.
U4SH6B.book Page 99 Tuesday, May 27, 2003 4:39 PM

9-1
EBU00420
1-CLEANING AND STORAGE
A. CLEANING
Frequent, thorough cleaning of your machine will
not only enhance its appearance but will improve
its general performance and extend the useful life
of many components.
1. Before cleaning the machine:
a. Block off the end of the exhaust pipe to pre-
vent water entry. A plastic bag and strong
rubber band may be used.
b. Make sure the spark plug and all filler caps
are properly installed.
2. If the engine case is excessively greasy, ap-
ply degreaser with a paint brush. Do not ap-
ply degreaser to the wheel axles.
3. Rinse the dirt and degreaser off with a garden
hose. Use only enough pressure to do the
job.
U4SH6B.book Page 1 Tuesday, May 27, 2003 4:39 PM