2003 YAMAHA WARRIOR 350 engine

8-19 1. Oil filter cover 2. Bolt (× 3)
3. Oil filter 4. O-ring
1. Couvercle du filtre à huile 2. Boulon (× 3)
3. Filtre à huile 4. Joint torique
1. Tapa del filtro de aceite 2. Perno (× 3)
3. Filtro de aceite 4. Junta tórica
5. Remove the oil filter cover by removing the
bolts and then remove the oil filter element.
6. Clean the oil strainer and oil filter element
with solvent.
7. Check the O-ring for damage and replace it if
damaged.
8. Install the oil filter element, and O-ring.
9. Install the oil filter cover by installing the bolts.
10. Install the oil strainer, compression spring
and drain bolt. Tighten the drain bolt and oil
filter cover bolts to the specified torques.CAUTION:_ Before installing the drain bolt, be sure to in-
stall the O-ring, compression spring and oil
strainer. _11. Fill the engine with oil, and then install the
dipstick. Tightening torques:
Drain bolt (engine):
32 Nm (3.2 m·kgf)
Filter cover bolt:
10 Nm (1.0 m·kgf)
U5NF61.book Page 19 Wednesday, June 13, 2001 5:18 PM

8-21
CAUTION:
Be sure no foreign material enters the crank-
case. 12. Warm up the engine for several minutes at
idle speed. Check for oil leakage while warm-
ing up.CAUTION:
If oil leakage is found, stop the engine immedi-
ately and check for the cause. Recommended oil:
See page 10-2.
Oil quantity:
Periodic oil change:
2.4 L
With oil filter replacement:
2.5 L
Total amount:
3.2 L
U5NF61.book Page 21 Wednesday, June 13, 2001 5:18 PM

8-23 1. Oil gallery bolt
1. Boulon de rampe de graissage
1. Perno del conducto de aceite
Oil pressure check
1. Put a cloth around the cylinder.
2. Slightly loosen the oil gallery bolt in the cylin-
der head.
3. Start the engine and keep it idling until oil be-
gins to seep from the oil gallery. If no oil
comes out after one minute, turn the engine
off so it will not seize and find the cause.
4. Start the engine, and then check the oil pres-
sure.
5. After checking, tighten the oil gallery bolt to
the specified torque.CAUTION:_ Be sure to check the oil pressure after replac-
ing the engine oil. _
Tightening torque:
Oil gallery bolt:
7 Nm (0.7 m·kgf)
U5NF61.book Page 23 Wednesday, June 13, 2001 5:18 PM

8-25
EBU00870
Spark plug 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.
For example, a very white center electrode porce-
lain color could indicate an intake air leak or carbu-
retion 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 elec-
trode erosion becomes excessive, you should re-
place the spark plug with one of the proper type.
Standard spark plug:
DR8EA (NGK)
U5NF61.book Page 25 Wednesday, June 13, 2001 5:18 PM

8-29 1. Check hose
1. Flexible de contrôle
1. Manguito de comprobación
1. Air filter case cover
2. Screw (× 5)
1. Couvercle du boîtier de filtre à air
2. Vis (× 5)
1. Tapa de la caja del filtro de aire
2. Tornillo (× 5)
EBU00950
Air filter cleaningNOTE:_ There is a check hose at the bottom of the air filter
case. If dust or water collects in this hose, empty
the hose and clean the air filter element and air fil-
ter case. _1. Remove the seat.
2. Remove the air filter case cover by removing
the screws.
3. Remove the air filter element, and separate it
from the guide.
4. Wash the element gently but thoroughly 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 explode. _5. 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. _
U5NF61.book Page 29 Wednesday, June 13, 2001 5:18 PM

8-31 1. Unlock
1. Déverrouiller
1. Levántelo
1. Element retaining plate 2. Guide
3. Air filter element
1. Plaquette de retenue d’élément 2. Guide
3.Élément du filtre à air
1. Placa de retención del elemento 2. Guía
3. Elemento del filtro de air
6. Inspect the air filter element. If damaged, re-
place it.
7. Apply SAE 10W30 motor oil to the air filter el-
ement.NOTE:_ The element should be wet but not dripping. _8. Apply all-purpose grease to the air filter ele-
ment seat.
9. Install the air filter element on the guide.
10. Install the air filter element assembly and
parts removed for access.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 filter case for
obstructions. Check the air cleaner rubber joint to
the carburetor and manifold fittings for an airtight
seal. Tighten all fittings securely to avoid the pos-
sibility of unfiltered air entering the engine.
U5NF61.book Page 31 Wednesday, June 13, 2001 5:18 PM

8-33
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.
U5NF61.book Page 33 Wednesday, June 13, 2001 5:18 PM

8-35 1. Throttle stop screw
1. Vis de butée de papillon
1. Tornillo de tope del acelerador
EBU00301
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 and set the idle to
the specified idling speed by adjusting the
throttle stop screw. Turn the screw in to in-
crease engine speed, and out to decrease
engine speed.
Specified idle speed:
1,450 ~ 1,550 r/min
U5NF61.book Page 35 Wednesday, June 13, 2001 5:18 PM