2014 YAMAHA YZ450F engine

CABLE ROUTING DIAGRAM
2-34
1. Clutch cable
2. Throttle cable (pull)3. Throttle cable (return)
4. Cable holder
5. Engine stop switch lead6. Frame
7. Coupler for connecting optional part
8. Bracket9. Engine stop switch coupler
10. Rectifier/regulator coupler
11. Starter knob/idle screw12. Neutral switch lead
13. Crankcase cover
14. AC magneto lead15. Front engine bracket
16. Radiator hose
17. Coupler cover18. Rectifier/regulator lead
19. Tension arm
20. Main harness21. Tank rail
22. Radiator
23. Cylinder head breather hose24. Radiator breather hose
25. Down tube
26. Crankcase
A. Pass the engine stop switch lead between the
frame and the cable holder.
B. Pass the engine stop switch lead between the
coupler for connecting optional part and the
frame, where the main harness should face the
outside of the vehicle.
C. Insert the coupler for connecting optional part into
the connector, and fix it to the bracket.
D. Insert and fix the engine stop switch coupler to
the bracket.
E. Insert and fix the rectifier/regulator coupler to the
bracket.
F. Pass the AC magneto lead to the front of the ve-hicle beyond the starter knob/idle screw and to
the rear of the vehicle beyond the radiator. No
pinch is allowed between the radiator and the
tension arm.
G. 70 mm (2.76 in)
H. Bring the neutral switch lead into line with the
crankcase cover with no sag allowed.
I. Bring the AC magneto lead into line with the
clutch cable with no sag allowed.
J. Pass the neutral switch lead to the inside of the
front engine bracket (the side of the vehicle).
K. Clamp the clutch cable and the AC magneto lead
by the plastic locking tie. Regardless of the orien-tation of the lock on the plastic locking tie, cut the
end.
L. Pass the clutch cable with no downward sag al-lowed.
M. Bring the grommet of the clutch cable into contact
with the radiator hose, and pass it to the outside
of the neutral switch lead and the AC magneto
lead (the outside of the vehicle).
N. 40 mm (1.57 in)
O. Clamp the clutch cable, the AC magneto lead,
and the neutral switch lead by the plastic locking
tie. Make sure that they are clamped at the posi
-tioning tape in the clutch cable. Make the lock on
the plastic locking tie face the front of the vehicle,
and cut the end.
P. After connecting the neutral switch coupler, at-tach the coupler cover.Q. After connecting the AC magneto coupler, attach
the coupler cover.
R. Pass the rectifier/regulator lead to the inside of
the tension arm (the side of the vehicle).
S. Pass the main harness to the front of the radiator
hose (the front of the vehicle), and to the inside of
the clutch cable (the side of the vehicle).
T. Pass the engine stop switch lead between the
coupler for connecting optional part and the tank
rail, with the lead on the main harness side facing
the top of the vehicle.
U. Pass the radiator breather hose between the
down tubes.
V. Clamp the radiator breather hose, above the en-gine bracket (front). Clamp the lock on the plastic
tie with it located outside the vehicle, and face the
end toward the front of the vehicle.
W. Clamp the clutch cable at the front of the lead (the
front of the vehicle).
X. Make the lock on the plastic locking tie face the
front of the vehicle, and insert the projection into
the hole in the frame. Cut the end of the plastic
locking tie.

CABLE ROUTING DIAGRAM
2-36
1. Bracket
2. Condenser3. Coolant temperature sensor
4. Coupler cover
5. Intake air temperature sensor coupler6. Intake air temperature sensor coupler
7. Radiator hoses
8. Radiator breather hose9. Joint coupler
10. Plate
11. Tension arm12. Throttle position sensor lead
13. Ground lead
14. Throttle position sensor coupler15. Radiator breather hose
16. Cylinder head breather hose
17. Engine guard18. Crankcase
19. Fuel pump coupler
20. Fuel hose21. Condenser lead
22. Fuel pump lead
23. Condenser coupler24. Ground lead terminal
25. Fuel tank
26. Damper27. Rear frame
28. Main harness
A. Insert the condenser into the bracket as far as it
will go.
B. Attach the coupler cover to the coolant tempera-ture sensor coupler.
C. Pass the radiator breather hose to the inside of
the radiator hose (the side of the vehicle).
D. Insert and fix the joint coupler to the plate. After
fixing it, attach the cover.
E. Pass the throttle position sensor lead to the out-side of the tension arm (the outside of the vehi-cle).
F. After connecting the throttle position sensor cou-pler, attach the cover.
G. Pass the radiator breather hose to the outside of
the tension arm and the throttle position sensor
lead (the outside of the vehicle), and to the inside
of the radiator hose (the side of the vehicle).
H. Pass the protector of the cylinder head breather
hose until it touches the holder.
I. Pass the cylinder head breather hose between
the engine guard and the crankcase.
J. Install the end of the cylinder head breather hose
with it facing downward.
K. After connecting the fuel pump coupler, attach
the coupler cover.
L. 55 mm (2.17 in) (seat load receiver)
M. Clamp the fuel hose and the fuel pump lead by
the holder. Make sure that the painted part on the
fuel hose is clamped, and face the lock on the
clamp toward the rear top of the vehicle.
N. Do not install the plastic locking tie to the seat
load receiver.
O. Make the lock on the plastic locking tie face the
front of the vehicle, and make the end face the
bottom of the vehicle. Do not cut the end.
P. Install the ground lead terminal between the plate
and the bolt.
Q. DetentR. Fix the ground lead terminal to the detent in the
plate. For the ground lead terminal, either side
will do.
S. Insert the projection on the plastic locking tie into
the hole in the rear frame.
T. Clamp the painted part on the fuel hose by the
plastic clamp. Make the lock on the plastic clamp
face the bottom of the vehicle, and cut the end.

CABLE ROUTING DIAGRAM
2-38
1. Throttle cable
2. Clutch cable3. Engine stop switch lead
4. Cable guide
5. Head pipe6. Front brake hose
7. Brake hose guide
8. Number plate
A. Number plate band
B. Pass the clutch cable to the rear of the number
plate band.
C. Clamp the engine stop switch lead to the handle-bar by the plastic band. Do not cut the end of the
plastic band.
D. Pass the engine stop switch lead between the
head pipe and the cable guide.
E. Pass the front brake hose to the front of the num-ber plate.
F. 40°±10°G. Vertical direction
H. Pass the engine stop switch lead under the han-dlebar.
I. Pass the clutch cable to the guide in the number
plate.

3
PERIODIC CHECKS AND ADJUSTMENTS
MAINTENANCE INTERVALS.......................................................................... 3-1
MAINTENANCE INTERVALS .................................................................... 3-1
PRE-OPERATION INSPECTION AND MAINTENANCE................................. 3-7
GENERAL INSPECTION AND MAINTENANCE........................................ 3-7
ENGINE............................................................................................................ 3-8
CHECKING THE COOLANT LEVEL .......................................................... 3-8
CHECKING THE COOLING SYSTEM ....................................................... 3-8
CHANGING THE COOLANT...................................................................... 3-8
CHECKING THE RADIATOR CAP ............................................................ 3-9
CHECKING THE RADIATOR CAP OPENING PRESSURE ...................... 3-9
CHECKING THE COOLANT CIRCULATORY SYSTEM FOR LEAKS .... 3-10
ADJUSTING THE CLUTCH LEVER POSITION ...................................... 3-10
ADJUSTING THE CLUTCH LEVER FREE PLAY .................................... 3-10
ADJUSTING THE THROTTLE GRIP FREE PLAY .................................. 3-11
LUBRICATING THE THROTTLE CABLE ................................................ 3-12
CLEANING THE AIR FILTER ELEMENT................................................. 3-12
CHECKING THE THROTTLE BODY JOINT ............................................ 3-13
CHECKING THE BREATHER HOSES .................................................... 3-13
CHECKING THE EXHAUST SYSTEM..................................................... 3-13
CHECKING THE FUEL LINE ................................................................... 3-14
CHECKING THE ENGINE OIL LEVEL..................................................... 3-14
CHANGING THE ENGINE OIL ................................................................ 3-15
ADJUSTING THE ENGINE IDLING SPEED ............................................ 3-16
ADJUSTING THE VALVE CLEARANCE ................................................. 3-17
CHASSIS........................................................................................................ 3-21
BLEEDING THE BRAKE SYSTEM .......................................................... 3-21
CHECKING THE BRAKE HOSE .............................................................. 3-22
ADJUSTING THE FRONT BRAKE .......................................................... 3-22
ADJUSTING THE REAR BRAKE ............................................................. 3-23
CHECKING THE FRONT BRAKE PADS ................................................. 3-23
CHECKING THE REAR BRAKE PADS ................................................... 3-25
CHECKING THE REAR BRAKE PAD INSULATOR ................................ 3-26
CHECKING THE BRAKE FLUID LEVEL.................................................. 3-26
ADJUSTING THE DRIVE CHAIN SLACK ................................................ 3-27
CHECKING THE FRONT FORK LEGS ................................................... 3-28
CHECKING THE FRONT FORK PROTECTOR GUIDE .......................... 3-28
CLEANING THE FRONT FORK OIL SEAL AND DUST SEAL ................ 3-28
AIR BLEEDING FROM FRONT FORK .................................................... 3-28
ADJUSTING THE FRONT FORK LEGS .................................................. 3-29
CHECKING THE SWINGARM OPERATION ........................................... 3-30
CHECKING THE REAR SUSPENSION ................................................... 3-30
ADJUSTING THE REAR SHOCK ABSORBER ASSEMBLY ................... 3-30
CHECKING THE TIRES ........................................................................... 3-32
CHECKING AND TIGHTENING THE SPOKES ....................................... 3-32
CHECKING THE WHEELS ...................................................................... 3-33

MAINTENANCE INTERVALS
3-1
EAS1SL1065
MAINTENANCE INTERVALS
EAS1SL1066MAINTENANCE INTERVALSECA@
NOTICE
• After a break-in or before each race, always check the points shown in “TORQUE-CHECK
POINTS” for tightening torques and retighten them. (
“TORQUE-CHECK POINTS” on page 1-
25.)
• Periodic inspection is essential in making full use of the machine performance. The life of
parts varies significantly according to the environment in which the machine runs (e.g., rain,
dirt, etc.). Therefore, earlier inspection is required by reference to the list below.
ITEM
After
break-
in
Every
race
(about
2.5
hours)Every
third
(about
7.5
hours)Every
fifth
(about
12.5
hours)
As re-
quiredRemarks
VALVE
Check the valve
clearancesThe engine must be cold.
InspectCheck the valve seats and the
valve faces for wear.
Replace
VALVE SPRING
InspectCheck the free length and the
tilt.
Replace
VALVE LIFTER
InspectCheck for scratches and wear.
Replace
CAMSHAFTInspect the camshaft surface.
InspectInspect the decompression
system.
Replace
CAMSHAFT
SPROCKET
InspectCheck for wear on the teeth
and for damage.
Replace
PISTON
InspectInspect crack.
CleanInspect carbon deposits and
eliminate them.
ReplaceReplace the piston, piston pin,
piston pin clip, and piston ring
all as a set.

MAINTENANCE INTERVALS
3-2
PISTON RING
InspectCheck the end gap of the pis-
ton ring.
ReplaceReplace the piston, piston pin,
piston pin clip, and piston ring
all as a set.
PISTON PIN
Inspect
ReplaceReplace the piston, piston pin,
piston pin clip, and piston ring
all as a set.
CYLINDER HEADCheck the coolant passages
for corrosion.

Inspect carbon deposits and
eliminate them.
Inspect and cleanCheck for warpage, and re-
place the gasket.
CYLINDER
Inspect and cleanInspect score marks.
ReplaceInspect wear.
ENGINE OIL
InspectCheck the engine oil amount.
Replace
OIL FILTER ELE-
MENT
Replace
OIL STRAINER
Clean
CLUTCH
Inspect and adjustInspect housing, friction plate,
clutch plate and spring.
Replace
TRANSMISSION
Inspect
Replace bearings
SHIFT FORK, SHIFT
CAM, GUIDE BAR
InspectInspect wear.
ITEMAfter
break-
inEvery
race
(about
2.5
hours)Every
third
(about
7.5
hours)Every
fifth
(about
12.5
hours)As re-
quiredRemarks

MAINTENANCE INTERVALS
3-3
NUT (ROTOR)
RetightenCheck for tightening torques.
EXHAUST PIPE, SI-
LENCER, PROTEC-
TOR
Inspect and re-
tighten
Check for exhaust leaks, and
tightening torques.
Clean
Replace fiver*
* When the exhaust sound be-
comes louder or when a per-
formance drop is felt.
CRANKSHAFT
Inspect and clean
THROTTLE BODY
Inspect
AIR FILTER
Clean and lubri-
cate
Use foam air-filter oil or equiv-
alent oil.
Replace
SPARK PLUG
Inspect and cleanCheck the electrodes and the
terminals for wear.
Replace
COOLING SYSTEM
Check coolant lev-
el and leakage
Check radiator cap
operationUse the radiator cap tester for
a checkup.
Check radiator cap
attached
Change the cool-
ant
Every two years
Inspect hoses
ENGINE GUARD
ReplaceBreakage
FRAME
Clean and inspect
ITEMAfter
break-
inEvery
race
(about
2.5
hours)Every
third
(about
7.5
hours)Every
fifth
(about
12.5
hours)As re-
quiredRemarks

PRE-OPERATION INSPECTION AND MAINTENANCE
3-7
EAS1SL1067
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.
EAS1SL1068GENERAL INSPECTION AND MAINTENANCE
TIP
Perform usual maintenance enough so that, in the race course, a confirmation of that and simple set-
ting adjustments may only be left, in order to get enough time to use effectively.
ITEMinspectPage
CoolantCheck that coolant is filled up to the radiator cap.
Check the cooling system for leakage.3-8 – 10
FuelCheck that a fresh gasoline is filled in the fuel tank.
Check the fuel line for leakage.1-22
Engine oilCheck that the oil level is correct. Check the crank-
case and oil line for leakage.3-14 – 16
Gear shifter and clutchCheck that gears can be shifted correctly in order and
that the clutch operates smoothly.3-10 – 11
Throttle grip/Housing
Check that the throttle grip operation and free play
are correctly adjusted. Lubricate the throttle grip and
housing, if necessary.
3-11 – 12
BrakesCheck the play of front brake and effect of front and
rear brake.3-21 – 27
Drive chainCheck drive chain slack and alignment. Check that
the drive chain is lubricated properly.3-27
4-64 – 65
WheelsCheck for excessive wear and tire pressure. Check
for loose spokes and have no excessive play.3-32 – 33
SteeringCheck that the handlebar can be turned smoothly and
have no excessive play.3-33 – 34
Front forks and rear
shock absorberCheck that they operate smoothly and there is no oil
leakage.3-28 – 32
Cables (wires)
Check that the clutch and throttle cables move
smoothly. Check that they are not caught when the
handlebars are turned or when the front forks travel
up and down.
—
Exhaust pipeCheck that the exhaust pipe is tightly mounted and
has no cracks.3-13 – 14
Rear wheel sprocketCheck that the rear wheel sprocket tightening bolt is
not loose.4-8 – 9
LubricationCheck for smooth operation. Lubricate if necessary. 3-12 , 3-34
Bolts and nutsCheck the chassis and engine for loose bolts and
nuts.1-25 – 26
Lead connectorsCheck that the AC magneto, ECU and ignition coil are
connected tightly.1-12 – 14
Settings
Is the machine set suitably for the condition of the rac-
ing course and weather or by taking into account the
results of test runs before racing? Are inspection and
maintenance completely done?10-1 – 8