2007 YAMAHA WR 450F fuel

4 - 89
ENGENGINE REMOVAL
EC4M0000
ENGINE REMOVAL
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the frame.
WARNING
Support the machine securely so there is nodanger of it falling over.
Drain the engine oil Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Seat, fuel tank and side cover Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Radiator Refer to “RADIATOR” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Air cut-off valve assembly Refer to “AIR INDUCTION SYSTEM”
section.
Clutch cable and guide Disconnect at the engine side.
Shift pedal Refer to “AC MAGNETO AND
STARTER CLUTCH” section.
Rear shock absorber Refer to “REAR SHOCK ABSORBER”
section in the CHAPTER 6
Carburetor Refer to “CARBURETOR” section.

5 - 60
CHASREAR SHOCK ABSORBER
EC580000
REAR SHOCK ABSORBER
Extent of removal:
1 Rear shock absorber removal
2 Rear shock absorber disassembly
Extent of removal Order Part name Q’ty Remarks
REAR SHOCK ABSORBER
REMOVAL
WARNING
Support the machine securely so there is nodanger of it falling over.Preparation for removal Hold the machine by placing the
suitable stand under the engine.
Seat and side covers Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
Silencer Refer to “EXHAUST PIPE AND
SILENCER” section in the CHAPTER 4.
Drain the coolant. Refer to “COOLANT REPLACEMENT”
section in the CHAPTER 3.
Catch tank breather hose Disconnect at the catch tank side.
Catch tank hose Disconnect at the catch tank side.
Air induction hose (air cut-off
valve-air filter case)Disconnect at the air filter case side.

–+ELEC
6 - 2
IGNITION SYSTEM
EC620000
IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
*1 marked: Refer to “FUSE INSPECTION” section in the CHAPTER 3.
*2 marked: Refer to “BATTERY INSPECTION AND CHARGING” section in the CHAPTER 3.
*3 marked: Only when the ignition checker is used.
NOTE:
•Remove the following parts before inspection.
1) Seat
2) Fuel tank
•Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket tester:
YU-3112-C/90890-03112
*1 Check fuse.Replace fuse and
check wire harness.
*2 Check battery Recharge or replace.
Spark gap test*3 Clean or replace
spark plug.
Check entire ignition
system for connection.
(couplers, leads and
ignition coil)Repair or replace.
Check “ENGINE STOP”
button.Replace.
Check main switch. Replace.
Check ignition coil. Primary coil Replace.
Secondary coil Replace.
Check AC magneto. Pick-up coil Replace.
Check neutral switch. Repair or replace.
Replace CDI unit.
OK
OK
No spark
OK
OK
OK
OK
OK
OK
Spark No good
No good
No good
No good
No good No good
No good
No good
No good

–+ELEC
6 - 16
CHARGING SYSTEM
EC680000
CHARGING SYSTEM
EC681001
INSPECTION STEPS
If the battery is not charged, use the following inspection steps.
*1 marked: Refer to “FUSE INSPECTION” section in the CHAPTER 3.
*2 marked: Refer to “BATTERY INSPECTION AND CHARGING” section in the CHAPTER 3.
NOTE:
•Remove the following parts before inspection.
1) Seat
2) Fuel tank
•Use the following special tool in this inspection.
Pocket tester:
YU-3112-C/90890-03112
*1 Check fuse.Replace fuse and
check wire harness.
*2 Check battery. Recharge or replace.
Check each coupler and
wire connection.Repair or replace.
Check charging voltage.Charging system is
good.
Check AC magneto. Charging coil Replace.
Replace rectifier/regulator.
OK
OK
OK
No good
OK
No good
No good No good
No good OK

–+ELEC
6 - 23
LIGHTING SYSTEM
LIGHTING SYSTEM
INSPECTION STEPS
Refer to the following flow chart when inspecting the lighting system for possible problems.
NOTE:
•Remove the following parts before inspection.
1) Seat
2) Fuel tank
3) Left side cover
•Use the following special tool in this inspection.
Check the bulb and bulb
socket.Replace the bulb
and/or bulb socket.
Check the taillight (LEDs).Replace the taillight
assembly.
Check the AC magneto. Lighting coil Replace.
Check the entire lighting
system proper for connec-
tions.Repair or replace.
Check the rectifier/regulator.Out-put
voltageReplace.
Pocket tester:
YU-3112-C/90890-03112
No good
OK
No good
OK
No good
OK
Improperly connected
OK
No good

7 - 1
TUN
EC700000
TUNING
EC710000
ENGINE
Carburetor setting
•The air/fuel mixture will vary depending on
atmospheric conditions. Therefore, it is nec-
essary to take into consideration the air pres-
sure, ambient temperature, humidity, etc.,
when adjusting the carburetor.
•Perform a test run to check for proper engine
performance (e.g., throttle response) and
spark plug(-s) discoloration or fouling. Use
these readings to determine the best possi-
ble carburetor setting.
NOTE:
It is recommended to keep a record of all car-
buretor settings and external conditions (e.g.,
atmospheric conditions, track/surface condi-
tions, lap times) to make future carburetor set-
ting easier.
WARNING
The carburetor is a part of the fuel line.
Therefore, be sure to install it in a well-
ventilated area, away from flammable
objects and any sources of fire.
Never look into the carburetor intake.
Flames may shoot out from the pipe if the
engine backfires while it is being started.
Gasoline may be discharged from the
accelerator pump nozzle when the carbu-
retor has been removed.
SETTING

7 - 2
TUN
CAUTION:
The carburetor is extremely sensitive to
foreign matter (dirt, sand, water, etc.).
During installation, do not allow foreign
matter to get into the carburetor.
Always handle the carburetor and its
components carefully. Even slight
scratches, bends or damage to carburetor
parts may prevent the carburetor from
functioning correctly. Carefully perform
all servicing with the appropriate tools
and without applying excessive force.
When the engine is stopped or when
riding at no load, do not open and close
the throttle unnecessarily. Otherwise, too
much fuel may be discharged, starting
may become difficult or the engine may
not run well.
After installing the carburetor, check that
the throttle operates correctly and opens
and closes smoothly.
Atmospheric conditions and carburetor
settings
The air density (i.e., concentration of oxygen
in the air) determines the richness or lean-
ness of the air/fuel mixture. Therefore, refer
to the above table for mixture settings.
That is:
•Higher temperature expands the air with its
resultant reduced density.
•Higher humidity reduces the amount of oxy-
gen in the air by so much of the water vapor
in the same air.
•Lower atmospheric pressure (at a high alti-
tude) reduces the density of the air.
Air temp. HumidityAir
pressure
(altitude)Mixture Setting
High High Low (high) Richer Leaner
Low Low High (low) Leaner Richer
SETTING

7 - 3
TUNSETTING
Effects of the setting parts on the throttle
valve opening
1Pilot jet
2Throttle valve cutaway
3Jet needle
4Main jet
ÈClosed
ÉFully open
1/2 3/4 1/4 1/8
1
2
3
4
ÈÉ
Main system
The FLATCR carburetor has a primary main
jet. This type of main jet is perfect for racing
machines since it supplies an even flow of fuel,
even at full load. Use the main jet and the jet
needle to set the carburetor.
1Jet needle
2Pilot air jet
3Needle jet
4Main jet
5Pilot jet