2006 YAMAHA YZ250F fuel

4 - 2
ENG
REMOVAL POINTS
Side cover
1. Remove:
Bolt (side cover)
Left side cover 1
Right side cover 2
NOTE:
Draw the side cover downward to remove it
because its claws a are inserted in the air fil-
ter case.
Number plate
1. Remove:
Bolt (number plate)
Number plate 1
NOTE:
The projection a is inserted into the band of
the number plate. Pull the band off the pro-
jection before removal.
Remove the hot starter cable 2 and clutch
cable 3 from the cable guide b on the num-
ber plate.
The projection c on the lower bracket is
inserted into the number plate. Remove the
number plate by pulling it off the projection.
ASSEMBLY AND INSTALLATION
Air scoop
1. Install:
Air scoop 1
Bolt (air scoop)
NOTE:
Put the portion a of the flap of the air filter
case on the inside of the air scoop.
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
SEAT, FUEL TANK AND SIDE COVERS

4 - 3
ENGEXHAUST PIPE AND SILENCER
EC4S0000
EXHAUST PIPE AND SILENCER
Extent of removal:
1 Silencer removal
2 Exhaust pipe removal
Extent of removal Order Part name Q’ty Remarks
EXHAUST PIPE AND
SILENCER REMOVAL
Preparation for removal Right side cover Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Bolt (silencer clamp) 1 Only loosening.
2 Bolt [silencer (front)] 1
3 Bolt [silencer (rear)] 1
4 Collar 1
5 Silencer 1
6 Silencer clamp 1
7 Nut (exhaust pipe) 1
8 Bolt (exhaust pipe) 1
9 Exhaust pipe 1
10 Gasket 2
2
1
2

4 - 6
ENGRADIATOR
EC450001
RADIATOR
Extent of removal:
1 Radiator removal
Extent of removal Order Part name Q’ty Remarks
RADIATOR REMOVAL
Preparation for removal Drain the coolant. Refer to “COOLANT REPLACEMENT”
section in the CHAPTER 3.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Radiator guard 2
2 Radiator hose clamp 10 Only loosening.
3 Radiator hose 1 1
4 Left radiator 1
5 Radiator hose 3 1
6 Radiator pipe 2 1
7 Radiator hose 5 1
8 Right radiator 1
9 Radiator hose 2 1
10 Radiator hose 4 1
11 Radiator breather hose 1
12 Radiator pipe 1 1
1

4 - 9
ENGCARBURETOR
CARBURETOR
3
97
8
4
4
2
T R..3 Nm (0.3 m • kg, 2.2 ft • Ib)
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..4 Nm (0.4 m •
kg, 2.9 ft • Ib)
T R..2 Nm (0.2 m •
kg, 1.4 ft • Ib)
T R..11 Nm (1.1 m •
kg, 8.0 ft • Ib)
5 1
6
6
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 - 12
ENGCARBURETOR
HANDLING NOTE
CAUTION:
Do not loosen the screws (throttle position
sensor)
1 except when changing the throt-
tle position sensor due to failure because it
will cause a drop in engine performance.
1
REMOVAL POINTS
Pilot screw
1. Remove:
Pilot screw 1
NOTE:
To optimize the fuel flow at a small throttle
opening, each machine’s pilot screw has been
individually set at the factory. Before removing
the pilot screw, turn it in fully and count the
number of turns. Record this number as the
factory-set number of turns out.
INSPECTION
Carburetor
1. Inspect:
Carburetor body
Contamination → Clean.
NOTE:
Use a petroleum based solvent for cleaning.
Blow out all passages and jets with com-
pressed air.
Never use a wire.

4 - 22
ENGCAMSHAFTS
CAMSHAFTS
CYLINDER HEAD COVER
Extent of removal:
1 Cylinder head cover removal
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD COVER
REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Spark plug 1
2 Cylinder head breather hose 1
3 Bolt (cylinder head cover) 2
4 Cylinder head cover 1
5 Cylinder head cover gasket 1
6 Timing chain guide (top side) 1
1

4 - 31
ENGCYLINDER HEAD
CYLINDER HEAD
Extent of removal:
1 Cylinder head removal
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Radiator hose 1 Disconnect at cylinder head side.
Carburetor Refer to “CARBURETOR” section.
Camshaft Refer to “CAMSHAFTS” section.
Upper engine bracket Refer to “ENGINE REMOVAL” section.
1 Radiator pipe 1
2 Oil delivery pipe 1
3Nut 2
4 Bolt [L = 135 mm (5.31 in)] 2
5 Bolt [L = 145 mm (5.71 in)] 2
6 Cylinder head 1
7 Timing chain guard (exhaust
side)1
1

4 - 80
ENGCDI MAGNETO
EC4L0000
CDI MAGNETO
Extent of removal:
1 CDI magneto removal
Extent of removal Order Part name Q’ty Remarks
CDI MAGNETO REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Disconnect the CDI magneto
lead.
Shift pedal Refer to “KICK SHAFT AND SHIFT
SHAFT” section.
1 Left crankcase cover 1
2 Nut (rotor) 1
Use special tool.
Refer to “REMOVAL POINTS”.
3 Rotor 1
4 Stator 1
5 Woodruff key 1
1