2015 YAMAHA YZ450F fuel

SPECIAL TOOLS
1-17
Pocket tester
90890-03112
Analog pocket tester
YU-03112-CThis tool is used to measure
the voltage, current, and re-
sistance of electrical compo-
nents.
Timing light
90890-03141
YU-03141This tool is used to measure
the ignition timing.
Pressure gauge
90890-03153
YU-03153This tool is used to measure
the fuel pressure.
Fuel pressure adapter
90890-03186
YM-03186This tool is used to mount the
pressure gauge.
Test harness S-pressure
sensor (3P)
90890-03207
YU-03207This tool is used to check the
throttle position sensor input
voltage.
FI diagnostic tool sub-lead
90890-03212
YU-03212This tool is used to connect
the Yamaha diagnostic tool
to a battery.
Yamaha diagnostic tool
90890-03231
Yamaha diagnostic tool (US)
90890-03234This tool is used to check er-
ror codes or carry out self-di-
agnosis.
Valve guide remover & in-
staller set (ø5.5)
90890-04016This tool is used to replace
the valve guide.
Valve guide remover (5.5
mm)
YM-01122
Valve guide installer (5.5
mm)
YM-04015
Valve guide reamer (5.5 mm)
YM-01196Tool name/Part number How to use Illustration

CONTROL FUNCTIONS
1-21
EAS1SL5039REAR BRAKE PEDAL
The rear brake pedal “1” is in the right of the
chassis. Press down on the brake pedal to ac-
tivate the rear brake.
EAS1SL5040STARTER KNOB/IDLE SCREW
Starting a cold engine requires a larger amount
of intake air, which is supplied by the starter
knob/idle screw “1”.
Pulling the knob toward “a” turns ON the start-
er, resulting in a larger amount of intake air.
Pushing the knob toward “b” turns OFF the
starter.
EWA@
WARNING
While handling the starter knob/idle screw,
take care not to burn yourself on exhaust
pipes.
EAS1SL5041FUEL TANK CAP
Fuel tank cap “1” is located under the fuel tank
cap cover “2”.
Remove the fuel tank cap cover to open the fuel
tank cap.
TIP
• To remove the fuel tank cap cover, insert fin-
gers under part “a”, and then use both hands
to lift it up towards the rear of the vehicle.
• Install the fuel tank cap cover after placing the
bands “3” all the way in under the seat.
1
ab1
1
23
a
2

STARTING AND BREAK-IN
1-22
EAS1SL5042
STARTING AND BREAK-IN
EAS1SL5043FUEL
Always use the recommended fuel as stated
below. Also, be sure to use new gasoline the
day of a race.
JCA
NOTICE
Use only unleaded gasoline. The use of
leaded gasoline will cause severe damage
to the engine internal parts such as valves,
piston rings, and exhaust system, etc.
TIP
Your Yamaha engine has been designed to use
premium unleaded gasoline with a pump oc-
tane number [(R+M)/2] of 91 or higher, or a re-
search octane number of 95 or higher. If
knocking (or pinging) occurs, use a gasoline of
a different brand.
JWA
WARNING
• For refueling, be sure to stop the engine
and use enough care not to spill any fuel.
Also be sure to avoid refueling close to a
fire.
• Refuel after the engine, exhaust pipe, etc.
have cooled off.
Gasohol (For USA and Canada)
There are two types of gasohol: gasohol con-
taining ethanol and that containing methanol.
Gasohol containing ethanol can be used if the
ethanol content does not exceed 10%. Gasohol
containing methanol is not recommended by
Yamaha because it can cause damage to the
fuel system or vehicle performance problems.
EAS1SL5044STARTING A COLD ENGINE
1. Press the shift pedal to neutral.
2. Pull the starter knob/idle screw “1” to its full
length.
TIP
When the ambient temperature is 15°C (59°F)
or below, use the starter knob/idle screw.3. Push down the kickstarter lever lightly until
resistance is felt.
4. Fully close the throttle, and push down the
kickstarter lever in a stroke.
5. Immediately release the kickstarter lever.
EWA
WARNING
Do not open the throttle at the moment
when you kick the kickstarter lever, be-
cause this may kick back
TIP
If it fails to start, fully open the throttle grip and
give 10 to 20 slow kicks to clear the engine of
the rich air-fuel mixture retained in it.
6. When the engine starts running, warm this
up one or two minutes at a steady speed (of
3000 to 5000 r/min), and then return the
starter knob/idle screw to its original posi-
tion.
EWA
WARNING
Since exhaust gas contains harmful ingre-
dients, do not start or warm it up at an ill-
ventilated place or a closed narrow place. Recommended fuel
Premium unleaded gasoline
Fuel tank capacity
7.5 L (1.98 US gal, 1.65 lmp.gal)
1

STARTING AND BREAK-IN
1-23
7. To stop the engine, push the engine stop
switch “1”.
TIP
Continue pushing the engine stop switch till the
engine comes to a full stop.
EAS1SL5045STARTING A WARM ENGINE
When the engine is warm, give a kick with the
throttle closed without using the starter knob/
idle screw.
TIP
If it fails to start, fully open the throttle grip and
give 10 to 20 slow kicks to clear the engine of
the rich air-fuel mixture retained in it.
EAS1SL5046BREAK-IN PROCEDURES
A break-in is important so that rotating portion,
sliding surfaces, and mounted areas may fit
one another, and that the rider may become ac-
customed to the machine.
ECA
NOTICE
Before running, do maintenance on the air
filter element.
Refer to “CLEANING THE AIR FILTER ELE-
MENT” on page 3-12.
1. After warming up the engine, drive it for
about 20 minutes at a throttle opening of 1/2
or less.
2. Make a pit stop, and check mounted areas
for looseness, oil leaks, or other problems.
3. Then, drive it for about 40 minutes at a throt-
tle opening of 3/4 or less.
4. Make a pit stop again, and thoroughly check
mounted areas for looseness, oil leaks, or
other problems. Thorough checks and ad-
justments are required in particular for
stretch of cables, free play of the brake,
stretch of the drive chain, looseness of the
spoke, and so on.
ECA
NOTICE
After a break-in or after each race, always
check the points shown in “TORQUE-
CHECK POINTS” for tightening torques and
retighten them. (Refer to “TORQUE-CHECK
POINTS” on page 1-25.)
Also when the following parts are replaced,
a break-in is required.
• Cylinder and Crankshaft: A break-in is re-
quired for about an hour.
• Piston, Piston ring, Valve, Camshaft, and
Gear: A break-in is required for about 30
minutes at a throttle opening of 1/2 or less.
Observe the condition of the engine careful-
ly during a break-in.
For checkpoints for a break-in, see “MAIN-
TENANCE AFTER BREAK-IN”. If any prob-
lem is found, immediately stop the engine
and make a checkup.

MAINTENANCE AFTER BREAK-IN
1-24
EAS1SL5047
MAINTENANCE AFTER BREAK-IN
After a break-in, perform careful maintenance
to get ready for the next practice or race.
Refer to “PRE-OPERATION INSPECTION
AND MAINTENANCE” on page 3-7.
EAS1SL5048MAJOR MAINTENANCE
1. For the engine
• Leaks around the engine
Check for pressure leaks from the cylinder
head or the cylinder, oil leaks from the
crankcase or the case cover, leaks from the
coolant system, and other leaks.
• Check that the valve, the cylinder head, the
cylinder, the piston, and the piston ring fit
one another, and that contact between the
valve and the cylinder head, and that be-
tween the cylinder and the piston are cor-
rect.
• Engine oil change
Drain the oil, and check for dirt and foreign
materials such as metal chips. (If any foreign
material is mixed, disassemble and check
the crankcase.)
Pour the specified amount of the recom-
mended oil.
• AC magneto
Check for looseness in mounted areas of
the rotor and the stator.
Check that the connector is not being dis-
connected.
• Silencer
Check the main body and stay for cracks.
Check for leaks.
• Mounting bolts and nuts
Check for looseness in mounted areas of
parts, as well as engine mounting bolts and
engine brackets.
2. For the chassis
• Check welds and mounted areas of the
frame, the swingarm, the link, the bracket,
and so on, for looseness and cracks.
• Wheel (s)
Check the wheel for runout. Check the
spoke for looseness.
• Brake(s)
Check the brake disc mounting bolt for
looseness.
Check that the reservoir contains the speci-
fied amount of brake fluid. Check for leaks.• Cable
Grease and adjust cables.
•Drive chain
Lubricate the drive chain and adjust its ten-
sion.
• Fuel tank
Clean the inside of the fuel tank. Check for
leaks.
• Suspension
Check for oil leaks in the front fork or the rear
shock absorber. Check that the mounted
conditions are good.
• Sprocket
Check for looseness in the sprocket mount-
ed on the rear wheel.
• Mounting bolts and nuts
Check mounted areas for looseness.
JCA1SL1001
NOTICE
After a break-in or before each race, always
check the points shown in “TORQUE-
CHECK POINTS” for tightening torques and
retighten them. (Refer to “TORQUE-CHECK
POINTS” on page 1-25.)
• Greasing and oiling
Always grease or oil the specified points.

TORQUE-CHECK POINTS
1-25
EAS1SL5049
TORQUE-CHECK POINTS
Frame construction Frame to rear frame
Frame to engine protector
Combined seat and fuel tank Fuel tank to frame
Engine mounting Frame to engine
Engine bracket to engine
Engine bracket to frame
Seat Seat to frame
Steering Steering stem to handlebar Steering stem to frame
Steering stem to upper bracket
Upper bracket to handlebar
Suspension Front Steering stem to front fork Front fork to upper bracket
Front fork to lower bracket
Rear Link Assembly of links
Link to frame
Link to rear shock absorber
Link to swingarm
Mounting of rear shock absorber Rear shock absorber and frame
Mounting of swingarm Tightening of pivot shaft
Wheel (s) Mounting of wheel Front Tightening of wheel axle
Tightening of axle holder
Tightening of spoke nipple
Rear Tightening of wheel axle
Wheel to rear wheel sprocket
Tightening of spoke nipple
Brake(s) Front Brake caliper to front fork
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to handle-
bar
Tightening of bleed screw
Tightening of brake hose holder
Rear Brake pedal to frame
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to frame
Tightening of bleed screw
Tightening of brake hose holder
Fuel system Fuel pump to fuel tank
Plastic cover Tightening of number plate

CLEANING AND STORAGE
1-27
EAS1SL5050
CLEANING AND STORAGE
EAS1SL5051CLEANING
Frequent cleaning of your vehicle will enhance
its appearance, maintain performance, and ex-
tend the life of parts.
1. Before cleaning, block the silencer outlet to
prevent water from entering. A plastic bag
secured with a rubber band may be used for
this purpose.
2. If the engine is contaminated with oil, apply
some degreaser to it with a brush. Do not
apply degreaser to the drive chain, the
sprockets, or the wheel axles.
3. Hose off dirt. Use only enough water pres-
sure to do the job.
ECA
NOTICE
Do not use high-pressure washers or steam
cleaners. Otherwise, these may cause a fail-
ure because of the entry of water.
4. After hosing off the dirt, wash all surfaces
with a mild detergent and warm water. Use
a toothbrush to clean hard-to-reach places.
5. Rinse the detergent with clean water, and
dry the surfaces with a soft towel or a cloth.
6. Immediately after cleaning, remove any wa-
ter from the drive chain with a paper towel,
and lubricate it to prevent rust.
7. Clean the seat with a vinyl upholstery clean-
er to keep the cover pliable and glossy.
8. Automotive wax may be applied to all paint-
ed or chromed surfaces. Avoid using such
wax as contains abrasives, because it may
scratch surfaces.
9. After completing the above, start the engine
and allow it to warm up for several minutes.
EAS1SL5052STORAGE
If your vehicle is to be stored for 60 days or
more, some preventive measures must be tak-
en to avoid deterioration. After cleaning the ve-
hicle thoroughly, prepare it for storage as
follows:
1. Fill the fuel tank with gasoline.
2. Remove the spark plug, pour a spoonful of
engine oil (SAE 10W-40) into the spark plug
hole, and reinstall the plug. With the engine
stop switch pushed in, by pushing down the
kickstarter lever, crank the engine to coat
the cylinder walls with oil.3. Remove the drive chain, clean it thoroughly
with solvent, and lubricate it Reinstall the
drive chain or store it in a plastic bag tied to
the frame.
4. Lubricate all cables.
5. Lift up the frame of the vehicle to keep the
wheels off the ground.
6. Tie a plastic bag over the muffler outlet to
prevent moisture from entering.
7. If the vehicle is to be stored in a place that is
humid or exposed to the sea breeze, apply a
light coat of oil to metal surfaces. Do not ap-
ply oil to the seat or rubber parts.
TIP
Make any necessary repairs before the vehicle
is stored.

ENGINE SPECIFICATIONS
2-2
EAS1SL5054
ENGINE SPECIFICATIONS
Engine
Engine type Liquid cooled 4-stroke, DOHC
Displacement 450 cm
3
Cylinder arrangement Single cylinder
Bore  stroke 97.0  60.8 mm (3.8  2.4 in)
Compression ratio 12.5:1
Starting system Kickstarter
Fuel
Recommended fuel Premium unleaded gasoline only
Fuel tank capacity 7.5 L (1.98 US gal, 1.65 Imp.gal)
Engine oil
Lubrication system Wet sump
Recommended brand YAMALUBE
Type SAE 10W-30, SAE 10W-40, SAE 15W-40, SAE
20W-40 or SAE 20W-50
Recommended oil grade API service SG type or higher, JASO standard
MA
Engine oil quantity
Quantity (disassembled) 0.95 L (1.00 US qt, 0.84 Imp.qt)
With oil filter element replacement 0.69 L (0.73 US qt, 0.61 Imp.qt)
Without oil filter element replacement 0.67 L (0.71 US qt, 0.59 Imp.qt)
Oil filter
Oil filter type Paper
Oil pump
Oil pump type Trochoid
Inner-rotor-to-outer-rotor-tip clearance Less than 0.150 mm (0.0059 in)
Limit 0.20 mm (0.0079 in)
Outer-rotor-to-oil-pump-housing clearance 0.13–0.18 mm (0.0051–0.0071 in)
Limit 0.24 mm (0.0094 in)
Oil-pump-housing-to-inner-and-outer-rotor
clearance 0.06–0.11 mm (0.0024–0.0043 in)
Limit 0.17 mm (0.0067 in)
Cooling system
Radiator capacity (including all routes) 1.04 L (1.10 US qt, 0.92 Imp.qt)
Radiator capacity 0.57 L (0.60 US qt, 0.50 mp.qt)
Radiator cap opening pressure 108–137 kPa (1.08–1.37 kg/cm
2, 15.7–19.9
psi)
Radiator core
Width 112.6 mm (4.43 in)
Height 235.0 mm (9.25 in)
Depth 28.0 mm (1.10 in)
Water pump
Water pump type Single suction centrifugal pump
Spark plug
Manufacturer/model NGK/CR8E
Spark plug gap 0.7–0.8 mm (0.028–0.031 in)