2005 YAMAHA YZ250F carburetor

2 - 19
SPECCABLE ROUTING DIAGRAM
ÒMake sure that the throttle
position sensor coupler does
not go out side the chassis.
ÓFasten the throttle position
sensor lead.
ÔFasten the neutral switch lead
on the oil hose with a plastic
locking tie and cut off the tie
end.
ÕFasten the neutral switch lead.
ÖFasten the neutral switch lead,
CDI magneto lead and radiator
breather hose.
×Pass the neutral switch lead,
CDI magneto lead and radiator
breather hose between the
radiator and frame.ØPass the carburetor breather
hoses and overflow hose so
that all there hoses do not con-
tact the rear shock absorber.
B
E
C
9
B
C
C
9
0
0
A
0
0
0
0
B 0 Ì
Í
Î
Ï
Ð
Ð
Ñ
Ò
Ó
C
D
0 0 0E F
Ô Õ Ö ×
1
2
3
4
5 6 6 8
7
Ê
Ê ËÈ
É
AGG
H
Ø
D
F
C

3 - 2
INSP
ADJ
MAINTENANCE INTERVALS
SHIFT FORK, SHIFT CAM, GUIDE BAR
InspectInspect wear
ROTOR NUT
Retighten
EXHAUST PIPE, SILENCER, PRO-
TECTOR
Inspect and retighten
Clean
Replace * Whichever comes first
CRANK
Inspect and clean
CARBURETOR
Inspect, adjust and clean
SPARK PLUG
Inspect and clean
Replace
DRIVE CHAIN
Use chain lube
Chain slack: 48 ~ 58 mm
(1.9 ~ 2.3 in) Lubricate, slack, alignment
Replace
COOLING SYSTEM
Check coolant level and leakage
Check radiator cap operation
Replace coolant Every two years
Inspect hoses
OUTSIDE NUTS AND BOLTS Refer to “STARTING
AND BREAK-IN” section
in the CHAPTER 1. Retighten
AIR FILTER
Clean and lubricate
Use foam air-filter oil or
equivalent oil
Replace
OIL FILTER
Replace
OIL STRAINER (frame)
Clean
FRAME
Clean and inspect
FUEL TANK, COCK
Clean and inspect
BRAKES
Adjust lever position and pedal height
Lubricate pivot point
Check brake disc surface
Check fluid level and leakage
Retighten brake disc bolts, caliper
bolts, master cylinder bolts and union
bolts
Replace pads
Replace brake fluid Every one year
FRONT FORKS
Inspect and adjust
Replace oil Suspension oil “S1”
Replace oil sealItemAfter
break-inEvery
race
Every
third
(or
500 km)Every
fifth
(or
1,000 km)As re-
quiredRemarks


3

3 - 3
INSP
ADJ
MAINTENANCE INTERVALS
FRONT FORK OIL SEAL AND DUST
SEAL
Clean and lube Lithium base grease
PROTECTOR GUIDE
Replace
REAR SHOCK ABSORBER
(After
rain ride)
Inspect and adjust
Lube
Molybdenum disulfide
grease
Retighten
DRIVE CHAIN GUIDE AND ROLLERS
Inspect
SWINGARM
Molybdenum disulfide
grease
Inspect, lube and retighten
RELAY ARM, CONNECTING ROD
Molybdenum disulfide
grease
Inspect, lube and retighten
STEERING HEAD
Inspect free play and retighten
Clean and lube Lithium base grease
Replace bearing
TIRE, WHEELS
Inspect air pressure, wheel run-out,
tire wear and spoke looseness
Retighten sprocket bolt
Inspect bearings
Replace bearings
Lubricate Lithium base grease
THROTTLE, CONTROL CABLE Yamaha cable lube or
SAE 10W-30 motor oil
Inspect dirt and wear on
the throttle cable on the
carburetor side. Check routing and connection
Lubricate
Inspect and clean (throttle cable)
HOT STARTER, CLUTCH LEVER
Inspect free playItemAfter
break-inEvery
race
Every
third
(or
500 km)Every
fifth
(or
1,000 km)As re-
quiredRemarks

3 - 19
INSP
ADJ
VALVE CLEARANCE INSPECTION AND ADJUSTMENT
3. Remove:
Right radiator
Refer to “RADIATOR” section in the
CHAPTER 4.
Carburetor
Refer to “CARBURETOR” section in the
CHAPTER 4.
Spark plug
Upper engine bracket
Cylinder head cover
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
4. Remove:
Timing mark accessing screw 1
Crankshaft end accessing screw 2
O-ring
5. Check:
Valve clearance
Out of specification → Adjust.
Valve clearance (cold):
Intake valve:
0.10 ~ 0.15 mm
(0.0039 ~ 0.0059 in)
Exhaust valve:
0.17 ~ 0.22 mm
(0.0067 ~ 0.0087 in)

3 - 46
INSP
ADJ
ELECTRICAL/SPARK PLUG INSPECTION
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
Spark plug
2. Inspect:
Electrode 1
Wear/damage → Replace.
Insulator color 2
Normal condition is a medium to light tan
color.
Distinctly different color → Check the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure:
Plug gap a
Use a wire gauge or thickness gauge.
Out of specification → Regap.
4. Clean the plug with a spark plug cleaner if
necessary.
Spark plug gap:
0.7 ~ 0.8 mm (0.028 ~ 0.031 in)
5. Tighten:
Spark plug
NOTE:
Before installing a spark plug, clean the gas-
ket surface and plug surface.
Finger-tighten a the spark plug before torqu-
ing to specification b.
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)

4 - 8
ENGCARBURETOR
CARBURETOR
5 1
2
6
6 3
97
8
4
4
T R..3 Nm (0.3 m • kg, 2.2 ft  Ib)
T R..4 Nm (0.4 m 
kg, 2.9 ft  Ib)
T R..11 Nm (1.1 m 
kg, 8.0 ft  Ib)
T R..2 Nm (0.2 m 
kg, 1.4 ft  Ib)
T R..4 Nm (0.4 m 
kg, 2.9 ft  Ib)
T R..3 Nm (0.3 m  kg, 2.2 ft  Ib)
Extent of removal:
1 Carburetor removal
Extent of removal Order Part name Q’ty Remarks
CARBURETOR REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1Clamp 1
2 Throttle position sensor lead cou-
pler1
3 Throttle cable cover 1
4 Throttle cable 2
5 Clamp (air filter joint) 1 Loosen the screw (air filter joint).
6 Clamp (carburetor joint) 2 Loosen the screws (carburetor joint).
7 Hot starter plunger 1
8 Carburetor assembly 1
9 Carburetor joint 1
1

4 - 9
ENGCARBURETOR
EC468000
CARBURETOR DISASSEMBLY
Extent of removal:
1 Carburetor disassembly
Extent of removal Order Part name Q’ty Remarks
CARBURETOR DISASSEMBLY
1Carburetor breather hose 4
2Valve lever housing cover 1
3Screw (throttle shaft) 1
4Throttle valve 1
5Needle holder 1
6Jet needle 1
7Accelerator pump cover 1
8Spring 1
9Diaphragm (accelerator pump) 1
0Float chamber 1
ALeak jet 1
BPilot screw 1 Refer to “REMOVAL POINTS”.
CFloat pin 1
DFloat 1
ENeedle valve 1
1

4 - 10
ENGCARBURETOR
Extent of removal Order Part name Q’ty Remarks
FMain jet 1
GNeedle jet 1
HSpacer 1
IPilot jet 1
JStarter jet 1
KPush rod 1 Pull the push rod.
LThrottle shaft assembly 1
MPush rod link lever assembly 1
NPilot air jet 1
OCold starter plunger 1
1