YAMAHA YZ250F 2009 Manual PDF

4-1
SEAT, FUEL TANK AND SIDE COVERS
ENGINE
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles
(e.g., Yamaha dealers, service engineers, etc.) Those who have little knowledge and skill concerning servicing are request-
ed not to undertake inspection, adjustment, disassembly, or reassembly only by reference to this manual. It may lead to
servicing trouble and mechanical damage.
SEAT, FUEL TANK AND SIDE COVERS
REMOVING THE SEAT, FUEL TANK AND SIDE COVERS
Order Part name Q'ty Remarks
Turn the fuel cock to "OFF".
Disconnect the fuel hose.
1 Seat 1
2 Air scoop (left and right) 2
3 Bolt (fuel tank) 2
4 Fuel tank 1
5 Left side cover 1 Refer to removal section.
6 Right side cover 1 Refer to removal section.
7 Number plate 1 Refer to removal section.
4

4-2
SEAT, FUEL TANK AND SIDE COVERS
REMOVING THE SIDE COVER
1. Remove:
• Bolt (side cover)
• Left side cover "1"
• Right side cover "2"
Draw the side cover downward to re-
move it because its claws "a" are in-
serted in the air filter case.
REMOVING THE NUMBER PLATE
1. Remove:
• Bolt (number plate)
• Number plate "1"
• The projection "a" is inserted into
the band of the number plate. Pull
the band off the projection before
removal.
• Remove the hot starter cable "2"
and clutch cable "3" from the cable
guide "b" on the number plate.
• The projection "c" on the lower
bracket is inserted into the number
plate. Remove the number plate by
pulling it off the projection.
INSTALLING THE AIR SCOOP
1. Install
• Air scoop "1"
• Bolt (air scoop)
Put the portion "a" of the flap of the air
filter case on the inside of the air
scoop.
Bolt (air scoop):
7 Nm (0.7 m•kg, 5.1
ft•lb)

4-3
EXHAUST PIPE AND SILENCER
EXHAUST PIPE AND SILENCER
REMOVING THE EXHAUST PIPE AND SILENCER
Order Part name Q'ty Remarks
A. Except for USA and CDN
Right side coverRefer 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
4Collar 1
5 Silencer 1
6 Silencer clamp 1
7 Nut (exhaust pipe) 2
8 Exhaust pipe 1
9Gasket 2
10 Wave washer 3

4-4
EXHAUST PIPE AND SILENCER
CHECKING THE SILENCER AND
EXHAUST PIPE
1. Inspect:
•Gasket "1"
Damage→Replace.
CHANGING THE SILENCER FIBER
1. Remove:
• Rivet (front) "1"
• Inner pipe "2"
Take care not to damage the rivet
fitting holes (ø4.9 mm) "a" in re-
moval.
Pull out the inner pipe while lightly
tapping the stay "b" on the silencer
using a soft hammer.
2. Replace:
•Fiber "1"
3. Install:
•Inner pipe "1"
•Rivet (front) "2"
• Apply heat resistant sealant along
the plate edge "a" on the inside of
the silencer and also along the si-
lencer edge "b" as shown.
• Take care not to allow the fiber out
of place when installing the inner
pipe.
INSTALLING THE SILENCER AND
EXHAUST PIPE
1. Install:
•Gasket
• Exhaust pipe "1"
• Nut (exhaust pipe) "2"
First, temporarily install both nuts,
then tighten either of these nuts to 13
Nm (1.3 m•kg, 9.4 ft•lb) and the other
to 20 Nm (2.0 m•kg, 14 ft•lb), and
then come back to the first one and
retighten it to 20 Nm (2.0 m•kg, 14
ft•lb).
2. Install:
• Silencer clamp "1"
• Gasket "2"
• Silencer "3"
•Washer "4"
• Bolt (silencer) "5"
• Install the gasket with its meshed
area "a" toward the exhaust pipe
side.
• The gasket should be installed ac-
cording to the dimension shown.
Nut (exhaust pipe):
20 Nm (2.0 m•kg, 14
ft•lb)
Silencer clamp:
16 Nm (1.6 m•kg, 11
ft•lb)
Bolt (silencer):
30 Nm (3.0 m•kg, 22
ft•lb)
New

4-5
RADIATOR
RADIATOR
REMOVING THE RADIATOR
Order Part name Q'ty Remarks
Drain the coolant.Refer to "CHANGING THE COOLANT" sec-
tion in the CHAPTER 3.
Seat and fuel tankRefer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
1 Radiator guard 2
2 Radiator hose clamp 8 Only loosening.
3 Radiator hose 1 1
4 Left radiator 1
5 Radiator hose 3 1
6 Right radiator 1
7 Radiator hose 2 1
8 Radiator hose 4 1
9 Radiator breather hose 1
10 Radiator pipe 1 1

4-6
RADIATOR
HANDLING NOTE
Do not remove the radiator cap
when the engine and radiator are
hot. Scalding hot fluid and steam
may be blown out under pressure,
which could cause serious injury.
When the engine has cooled, open
the radiator cap by the following
procedure:
Place a thick rag, like a towel, over
the radiator cap, slowly rotate the
cap counterclockwise to the de-
tent. This procedure allows any re-
sidual pressure to escape. When
the hissing sound has stopped,
press down on the cap while turn-
ing counterclockwise and remove
it.
CHECKING THE RADIATOR
1. Inspect:
• Radiator core "1"
Obstruction→Blow out with com-
pressed air through rear of the ra-
diator.
Bent fin→Repair/replace.
INSTALLING THE RADIATOR
1. Install:
• O-ring "1"
• Radiator pipe 1 "2"
• Bolt (radiator pipe) "3"
Apply the lithium soap base grease
on the O-ring.
2. Install:
• Radiator breather hose "1"
• Radiator hose 2 "2"
• Radiator hose 3 "3"
• Radiator hose 4 "4"
To right radiator "5".3. Install:
• Right radiator "1"
• Bolt (right radiator) "2"
• Radiator hose 3 "3"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
4. Install:
• Left radiator "1"
• Bolt (left radiator) "2"
• Radiator hose 1 "3"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
5. Tighten:
• Radiator hose clamp "4"
6. Install:
• Radiator guard "1"
First fit the inner hook portion "a" and
then the outer one "b" onto the radia-
tor.
Bolt (radiator pipe):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (right radiator):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (left radiator):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Radiator hose 1:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Radiator hose clamp:
2 Nm (0.2 m•kg, 1.4
ft•lb)

4-7
CARBURETOR
CARBURETOR
REMOVING THE CARBURETOR
Order Part name Q'ty Remarks
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Rear shock absorber Refer to "REAR SHOCK ABSORBER" sec-
tion in the CHAPTER 5.
1Clamp 1
2 Throttle position sensor lead coupler 1
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) 1 Loosen the screws (carburetor joint).
7 Hot starter plunger 1
8 Carburetor assembly 1
9 Carburetor joint 1
4 Nm (0.4 m kg, 2.9 ft lb)
4 Nm (0.4 m kg, 2.9 ft lb)
2 Nm (0.2 m kg, 1.4 ft lb)
3 Nm (0.3 m kg, 2.2 ft lb)
3 Nm (0.3 m kg, 2.2 ft lb)
11 Nm (1.1 m kg, 8.0 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)

4-8
CARBURETOR
DISASSEMBLING THE CARBURETOR
Order Part name Q'ty Remarks
1 Carburetor breather hose 4
2 Valve lever housing cover 1
3 Screw (throttle shaft) 1
4 Throttle valve 1
5 Needle holder 1
6 Jet needle 1
7 Accelerator pump cover 1
8Spring 1
9 Diaphragm (accelerator pump) 1
10 Float chamber 1
11 Leak jet 1
12 Pilot screw 1 Refer to removal section.
13 Float pin 1
14 Float 1
15 Needle valve 1
16 Main jet 1
17 Needle jet 1
18 Spacer 1

4-9
CARBURETOR
19 Pilot jet 1
20 Starter jet 1
21 Push rod 1 Pull the push rod.
22 Throttle shaft assembly 1
23 Push rod link lever assembly 1
24 Pilot air jet 1
25 Cold starter plunger 1 Order Part name Q'ty Remarks

4-10
CARBURETOR
HANDLING NOTE
Do not loosen the screw (throttle
position sensor) "1" except when
changing the throttle position sen-
sor due to failure because it will
cause a drop in engine perfor-
mance.
REMOVING THE PILOT SCREW
1. Remove:
• Pilot screw "1"
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.
CHECKING THE CARBURETOR
1. Inspect:
• Carburetor body
Contamination→Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
2. Inspect:
•Main jet "1"
• Pilot jet "2"
• Needle jet "3"
• Starter jet "4"
• Pilot air jet "5"•Leak jet "6"
Damage→Replace.
Contamination→Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
CHECKING THE NEEDLE VALVE
1. Inspect:
• Needle valve "1"
• Valve seat "2"
Grooved wear "a" →Replace.
Dust "b" →Clean.
•Filter "c"
Clogged→Clean.
CHECKING THE THROTTLE
VALVE
1. Check:
• Free movement
Stick→Repair or replace.
Insert the throttle valve "1" into the
carburetor body, and check for free
movement.
CHECKING THE JET NEEDLE
1. Inspect:
• Jet needle "1"
Bends/wear→Replace.
• Clip groove
Free play exists/wear→Replace.
• Clip positionMEASURING AND ADJUSTING
THE FLOAT HEIGHT
1. Measure:
• Float height "a"
Out of specification→Adjust.
Measurement and adjustment
steps:
a. Hold the carburetor in an upside
down position.
• Slowly tilt the carburetor in the op-
posite direction, then take the mea-
surement when the needle valve
aligns with the float arm.
• If the carburetor is level, the weight
of the float will push in the needle
valve, resulting in an incorrect mea-
surement.
b. Measure the distance between
the mating surface of the float
chamber and top of the float using
a vernier calipers.
The float arm should be resting on the
needle valve, but not compressing
the needle valve.
c. If the float height is not within
specification, inspect the valve
seat and needle valve.
d. If either is worn, replace them
both.
e. If both are fine, adjust the float
height by bending the float tab "b"
on the float.
Standard clip position:
No.4 Groove
* No.5 Groove
* Except for USA and CDN
Float height:
8.0 mm (0.31 in)