2004 YAMAHA YZ250LC fuel

3-4
PRE-OPERATION INSPECTION AND MAINTENANCE
INSP
ADJ
EC320000
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
EC321000
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
Coolant Check that coolant is filled up to the radiator filler cap.
Check the cooling system for leakage.P3-5~9
Fuel Check that a fresh mixture of oil and gasoline is filled in
the fuel tank. Check the fuel line for leakage.P1-12
Transmission oil Check that the oil level is correct. Check the crankcase
for leakage.P3-12~14
Gear shifter and clutch Check that gears can be shifted correctly in order and
that the clutch operates smoothly.P3-9
Throttle grip/Housing Check that the throttle grip operation and free play
are correctly adjusted. Lubricate the throttle grip and P3-10~11
housing, if necessary.
Brakes Check the play of front brake and effect of front and
rear brake.P3-17~23
Chain Check chain slack and alignment. Check that the chain
is lubricated properly.P3-24~26
Wheels Check for excessive wear and tire pressure. Check for
loose spokes and have no excessive play.P3-34~35
Steering Check that the handlebar can be turned smoothly and
have no excessive play.P3-35~36
Front forks and Check that they operate smoothly and there is no oil
rear shock absorber leakage.P3-26~33
Cables (wires) Check that the clutch and throttle cables move smooth-
ly. Check that they are not caught when the handlebars —
are turned or when the front forks travel up and down.
Muffler Check that the muffler is tightly mounted and has no
cracks.P3-15~16
Sprocket Check that the driven sprocket tightening bolt is
not loose.P3-24
Lubrication Check for smooth operation. Lubricate if necessary. P3-37
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P1-16
Lead connectors Check that the CDI magneto, CDI unit, and ignition coil
are connected tightly.P1-6
Settings Is the machine set suitably for the condition of the
racing course and weather or by taking into account the
P7-1~24
results of test runs before racing? Are inspection and
maintenance completely done?
5XF-9-30-3A 4/21/03 2:09 PM Page 14

INSP
ADJ
3-14
PILOT AIR SCREW ADJUSTMENT
4. Remove:
9Oil drain bolt 1
9Oil filler cap 2
Drain the transmission oil.
5. Install:
9Aluminum washer
9Oil drain bolt 1
6. Fill:
9Transmission oil
Recommended oil:
Yamalube 4 (10W-30) or SAE
10W-30 type SE motor oil
Oil capacity
(periodic oil change):
0.75 L (0.66 Imp qt, 0.79 US qt)
20 Nm (2.0 m•kg, 14 ft•lb)
7. Check:
9Oil leakage
8. Check:
9Transmission oil level
9. Install:
9Oil filler cap 2
EC35L021
PILOT AIR SCREW ADJUSTMENT
1. Adjust:
9Pilot air screw 1
Adjusting steps:
9Turn in the pilot air screw until it is lightly
seated.
9Turn out the pilot air screw by the factory-set
number of turns.
NOTE:
To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot air screw has
been individually set at the factory. Before
adjusting the pilot air screw, turn it in fully and
count the number of turns. Record this num-
ber as the factory-set number of turns out.
Pilot air screw:
1 turn out
*7/8 turns out
(for reference only)
*For EUROPE
5XF-9-30-3A 4/21/03 2:09 PM Page 36

3-36
STEERING HEAD INSPECTION AND ADJUSTMENT
INSP
ADJ
9Loosen the ring nut one turn.
9Retighten the ring nut using the ring nut
wrench.
w
Avoid over-tightening.
9Check the steering shaft by turning it lock to
lock. If there is any binding, remove the
steering shaft assembly and inspect the
steering bearings.
9Install the plain washer 5, handle crown 6,
plain washer 7, steering shaft nut 8, han-
dlebar 9, handlebar holder 0 and number
plate q.
NOTE:
9The upper handlebar holder should be
installed with the punched mark aforward.
9Insert the end of fuel breather hose winto
the hole of the number plate.
cC
First tighten the bolts on the front side of
the handlebar holder, and then tighten the
bolts on the rear side.
Ring nut wrench:
YU-33975/90890-01403
Ring nut (initial tightening):
38 Nm (3.8 m•kg, 27ft•lb)
Steering shaft nut:
145 Nm (14.5 m•kg, 105 t•lb)
Handlebar upper holder:
28 Nm (2.8 m•kg, 20 ft•lb)
Pinch bolt (handle crown):
23 Nm (2.3 m•kg, 17 ft•lb)
Number plate:
7 Nm (0.7 m•kg, 5.1 ft•lb)
Ring nut (final tightening):
7 Nm (0.7 m•kg, 5.1 ft•lb)
5XF-9-30-3B 5/6/03 6:32 PM Page 36

3-39
IGNITION TIMING CHECK
INSP
ADJ
EC372012
IGNITION TIMING CHECK
1. Remove:
9Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
9Spark plug
9Crankcase cover (left)
2. Attach:
9Dial gauge 1
9Spark plug hole dial stand 2
3. Rotate the magneto rotor 1until the piston
reaches top dead center (TDC). When this
happens, the needle on the dial gauge will
stop and reverse directions even though the
rotor is being turned in the same direction.
4. Set the dial gauge to zero at TDC.
5. From TDC, rotate the rotor clockwise until
the dial gauge indicates that the piston is at
a specified distance from TDC.
6. Check:
9Ignition timing
Punch mark aon rotor should be aligned
with punch mark bon stator.
Not aligned Adjust.
Dial gauge:
YU-3097/90890-01252
Spark plug hole dial stand:
YU-1256
Ignition timing (B.T.D.C.):
0.18 mm (0.007 in)
5XF-9-30-3B 5/6/03 6:32 PM Page 42

4-1
SEAT, FUEL TANK AND SIDE COVERSENG
EC400000
ENGINE
EC4R0000
SEAT, FUEL TANK AND SIDE COVERS
Extent of removal Order Part name Q’ty Remarks
SEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Preparation for Turn the fuel cock to “OFF”.
removal Disconnect the fuel hose.
1 Seat 1
2 Air scoop (left and right) 2
3 Fitting band 1 Remove on fuel tank side.
4 Bolt (fuel tank) 2
5 Fuel tank 1
6 Side cover (left) 1
Refer to “REMOVAL POINTS”.
7 Side cover (right) 1
8 Number plate 1
1
4
Extent of removal:1Seat removal2Fuel tank removal
3Side covers removal4Number plate removal
2


 

3
7 Nm (0.7 m•kg, 5.1 ft•lb)
4 Nm (0.4 m•kg, 2.9 ft•lb)
4 Nm (0.4 m•kg, 2.9 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
19 Nm (1.9 m•kg, 13 ft•lb)
19 Nm (1.9 m•kg, 13 ft•lb)
5XF-9-30-4A 5/7/03 1:34 PM Page 2

4-2
ENGSEAT, FUEL TANK AND SIDE COVERS
EC4R3000
REMOVAL POINTS
EC413110
Side cover
1. Remove:
9Bolt (side cover)
9Side cover (left and right) 1
NOTE:
Draw the side cover downward to remove it
because its claws aare inserted in the air
cleaner case.
5XF-9-30-4A 5/7/03 1:34 PM Page 4

4-3
EXHAUST PIPE AND SILENCERENG
EC4S0000
EXHAUST PIPE AND SILENCER
Extent of removal:1Silencer removal2Exhaust pipe removal
11 Nm (1.1 m•kg, 8.0 ft•lb)
12 Nm (1.2 m•kg, 8.7 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
25 Nm (2.5 m•kg, 18 ft•lb)
12 Nm (1.2 m•kg, 8.7 ft•lb)
14 Nm (1.4 m•kg, 10 ft•lb)
Extent of removal Order Part name Q’ty Remarks
EXHAUST PIPE AND
SILENCER REMOVAL
Preparation for Side cover (right) Refer to “SEAT, FUEL TANK AND
removal SIDE COVERS” section.
1 Bolt (silencer) 2
2 Silencer 1
3 Collar [D=ø10.5 mm (0.41 in)] 1
4 Collar [D=ø10.0 mm (0.39 in)] 1
5 Grommet (front) 1
6 Grommet (rear) 1
7 Tension spring 2
8 Bolt (exhaust pipe) 2
9 Exhaust pipe 1
1
2
2
5XF-9-30-4A 5/7/03 1:34 PM Page 6

4-4
RADIATORENG
Extent of removal Order Part name Q’ty Remarks
RADIATOR REMOVAL
Preparation for Drain the coolant.
Refer to “COOLANT REPLACEMENT”
removal section in the CHAPTER 3.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section.
1 Panel 2
2 Clamp (radiator hose 2) 2 Only loosening.
3 Radiator hose 1 1
4 Radiator (left) 1
5 Radiator hose 4 1
6 Radiator (right) 1
7 Radiator hose 2 2
8 Radiator breather hose 1
EC450001
RADIATOR
Extent of removal:1Radiator removal
1
1 Nm (0.1 m•kg, 0.7 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
1 Nm (0.1 m•kg, 0.7 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
5XF-9-30-4A 5/7/03 1:35 PM Page 8