Front YAMAHA YZ450F 2014 Manual PDF

CYLINDER AND PISTON
5-33
EAS1SL1227REMOVING THE PISTON
1. Remove:
• Piston pin clip “1”
• Piston pin “2”
• Piston “3”ECA13810
NOTICE
Do not use a hammer to drive the piston pin
out.
TIP
• Before removing the piston pin clip, cover the
crankcase opening with a cloth to prevent the
piston pin clip from falling into the crankcase.
• Before removing the piston pin, deburr the
piston pin clip’s groove and the piston pin’s
bore area. If the piston pin groove is deburred
and the piston pin is still difficult to remove,
use the piston pin puller set “4”.
2. Remove:
• Top ring
• 2nd ring
• Oil ring
TIP
When removing a piston ring, open the end gap
with your fingers and lift the opposite end gap
of the piston ring over the piston crown.
EAS1SL1228CHECKING THE CYLINDER AND PISTON
1. Check:
• Piston wall (Sidewall)
• Cylinder wall
Vertical scratches  Replace the cylinder,
and replace the piston and piston rings as a
set.
2. Measure:
• Piston-to-cylinder clearance
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the cylinder bore with the cylinder
bore gauge.
TIP
Measure cylinder bore by taking side-to-side
and front-to-back measurements of the cylin
-
der. Then, find the average of the measure-
ments.
Piston pin puller set
90890-01304
Piston pin puller
YU-01304
1
Bore
97.000–97.010 mm (3.8189–
3.8193 in)
Taper limit
0.050 mm (0.0020 in)
Out of round limit
0.050 mm (0.0020 in)
Cylinder bore = maximum of D1–D6
Taper limit = (maximum of D1or D2) - (maxi-
mum of D5 or D6)
Out of round limit = maximum of D1, D3 or D5
- minimum of D
2, D4 or D6

CYLINDER AND PISTON
5-35
EAS1SL1230CHECKING THE PISTON PIN
1. Check:
• Piston pin
Blue discoloration/grooves  Replace the
piston pin and then check the lubrication
system.
2. Measure:
• Piston pin outside diameter “a”
Out of specification  Replace the piston
pin.
3. Measure:
• Piston pin bore inside diameter “b”
Out of specification  Replace the piston.
EAS1SL1231INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• 2nd ring “4”
• Top ring “5”
TIP
Be sure to install the piston rings so that the
manufacturer’s marks or numbers face up.
2. Install:
• Piston “1”
• Piston pin “2”
• Piston pin clip “3”
TIP
• Apply the engine oil to the piston pin.
• Install the piston with the F mark “a” on it
pointing to its intake (front) side.
• Before installing the piston pin clip, cover the
crankcase opening with a cloth to prevent the
clip from falling into the crankcase.
Piston ring end gap
Top ring
End gap (installed)
0.20–0.30 mm (0.0079–0.0118 in)
Limit
0.55 mm (0.0217 in)
End gap (installed)
0.35–0.50 mm (0.0138–0.0197 in)
Limit
0.85 mm (0.0335 in)
Oil ring
End gap (installed)
0.20–0.50 mm (0.0079–0.0197 in)
Piston pin outside diameter
17.991–18.000 mm (0.7083–
0.7087 in)
Limit
17.971 mm (0.7075 in)
Piston pin bore inside diameter
18.004–18.015 mm (0.7088–
0.7093 in)
Limit
18.045 mm (0.7104 in)
b
New

9
TROUBLE SHOOTING
TROUBLE SHOOTING..................................................................................... 9-1
GENERAL INFORMATION ........................................................................ 9-1
STARTING FAILURES ............................................................................... 9-1
INCORRECT ENGINE IDLING SPEED ..................................................... 9-1
POOR MEDIUM-AND-HIGH-SPEED PERFORMANCE ............................ 9-2
FAULTY GEAR SHIFTING ......................................................................... 9-2
SHIFT PEDAL DOES NOT MOVE ............................................................. 9-2
JUMPS OUT OF GEAR.............................................................................. 9-2
FAULTY CLUTCH ...................................................................................... 9-2
OVERHEATING ......................................................................................... 9-2
OVERCOOLING ......................................................................................... 9-3
POOR BRAKING PERFORMANCE ........................................................... 9-3
FAULTY FRONT FORK LEGS ................................................................... 9-3
UNSTABLE HANDLING ............................................................................. 9-3
LIST OF SELF-DIAGNOSTIC AND FAIL-SAFE ACTIONS............................. 9-4

TROUBLE SHOOTING
9-3
Fuel system
1. Throttle body
• Damaged or loose throttle body joint
2. Air filter
• Clogged air filter element
Chassis
1. Brake(s)
• Dragging brake
Electrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
2. Ignition system
• Faulty ECU
• Faulty coolant temperature sensor
EAS1SL1359OVERCOOLING
Cooling system
• Faulty coolant temperature sensor
EAS1SL1360POOR BRAKING PERFORMANCE
• Worn brake pad
• Worn brake disc
• Air in hydraulic brake system
• Leaking brake fluid
• Defective master cylinder kit
• Faulty brake caliper kit
• Faulty brake caliper seal
• Loose union bolt
• Damaged brake hose
• Oil or grease on the brake disc
• Oil or grease on the brake pad
• Incorrect brake fluid level
EAS1SL1361FAULTY FRONT FORK LEGS
Leaking oil
• Bent, damaged, or rusty inner tube
• Cracked or damaged outer tube
• Improperly installed oil seal
• Damaged oil seal lip
• Incorrect oil level (high)
• Loose damper rod assembly bolt
• Damaged damper rod assembly bolt copper
washer
• Cracked or damaged cap bolt O-ring
Malfunction
• Bent or damaged inner tube
• Bent or damaged outer tube
• Broken fork spring
• Bent or damaged damper rod
• Incorrect oil viscosity
• Incorrect oil level
EAS1SL1362UNSTABLE HANDLING
1. Handlebar
• Bent or improperly installed handlebar
2. Steering head components
• Improperly installed upper bracket
• Improperly installed lower bracket
(improperly tightened ring nut)
• Bent steering stem
• Damaged ball bearing or bearing race
3. Front fork leg (s)
• Uneven oil levels (both front fork legs)
• Unevenly tensioned fork spring (both front
fork legs)
• Broken fork spring
• Bent or damaged inner tube
• Bent or damaged outer tube
4. Swingarm
• Worn bearing or bushing
• Bent or damaged swingarm
5. Rear shock absorber assembly (-ies)
• Faulty rear shock absorber spring
• Leaking oil or gas
6. Tire (s)
• Uneven tire pressures (front and rear)
• Incorrect tire pressure
• Uneven tire wear
7. Wheel (s)
• Incorrect wheel balance
• Broken or loose spoke
• Damaged wheel bearing
• Bent or loose wheel axle
• Excessive wheel runout
8. Frame
• Bent frame
• Damaged steering head pipe
• Improperly installed bearing race

10
TUNING
CHASSIS........................................................................................................ 10-1
SELECTION OF THE SECONDARY REDUCTION 
RATIO (SPROCKET) .............................................................................. 10-1
DRIVE AND REAR WHEEL SPROCKETS SETTING PARTS ................ 10-1
TIRE PRESSURE..................................................................................... 10-2
FRONT FORK SETTING.......................................................................... 10-2
CHANGE IN AMOUNT AND CHARACTERISTICS OF FORK OIL.......... 10-2
SETTING OF SPRING AFTER REPLACEMENT .................................... 10-3
FRONT FORK SETTING PARTS............................................................. 10-3
REAR SUSPENSION SETTING .............................................................. 10-3
CHOOSING SET LENGTH ...................................................................... 10-3
SETTING OF SPRING AFTER REPLACEMENT .................................... 10-4
REAR SHOCK ABSORBER SETTING PARTS ....................................... 10-5
SUSPENSION SETTING (FRONT FORK)............................................... 10-6
SUSPENSION SETTING (REAR SHOCK ABSORBER) ......................... 10-7

CHASSIS
10-2
TIRE PRESSURE
Tire pressure should be adjusted to suit the
road surface condition of the circuit.
• Under a rainy, a muddy, a sandy, or a slippery
condition, the tire pressure should be lower
for a larger area of contact with the road sur
-
face.
• Under a stony or a hard road condition, the
tire pressure should be higher to prevent a flat
tire.
EAS1SL1369FRONT FORK SETTING
The front fork setting should be made depend-
ing on the rider's feeling of an actual run and
the circuit conditions.
The front fork setting includes the following
three factors:
1. Setting of air spring characteristics
• Change the fork oil amount.
2. Setting of spring preload
• Change the spring.
3. Setting of damping force
• Change the compression damping force.
• Change the rebound damping force.
The spring acts on the load and the damping
force acts on the cushion travel speed.
EAS1SL1370CHANGE IN AMOUNT AND CHARACTERIS-
TICS OF FORK OIL
Damping characteristic near the final stroke
can be changed by changing the fork oil
amount.
EWA1DX4001
WARNING
Adjust the oil amount in 5 cm3 (0.2 US oz,
0.2 Imp. oz) increments or decrements. Too
small oil amount causes the front fork to
produce a noise at full rebound or the rider
to feel some pressure on his hands or body.
Alternatively, too large oil amount will
cause the air spring characteristics to have
a tendency to be stiffer with the consequent
deteriorated performance and characteris
-
tics. Therefore, adjust the front fork within
the specified range.
EAS1SL1371
Standard tire pressure
100 kPa (1.0 kgf/cm2,15 psi)
Extent of adjustment
60–80 kPa (0.6–0.8 kgf/cm2, 9.0–
12 psi)
Extent of adjustment
100–120 kPa (1.0–1.2 kgf/cm2,
15–18 psi)
Standard oil amount
335 cm3 (11.33 US oz, 11.82
lmp.oz) (USA) (CAN)
355 cm3 (12.00 US oz, 12.52
lmp.oz) (EUR) (JPN) (AUS) (NZL)
(ZAF)
Extent of adjustment
300–365 cm3 (10.14–12.34 US
oz, 10.58–12.87 Imp. oz)
A. Air spring characteristics in relation to oil
amount change
B. Load
C. Stroke
1. Max. oil amount
2. Standard oil amount
3. Min. oil amount

CHASSIS
10-3
SETTING OF SPRING AFTER REPLACE-
MENT
As the front fork setting can be easily affected
by the rear suspension, take care so that the
front and the rear are balanced (in position etc.)
when setting the front fork.
1. Use of soft spring
• Change the rebound damping force.
Turn out one or two clicks.
• Change the compression damping force.
Turn in one or two clicks.
TIP
Generally a soft spring gives a soft riding feel-
ing. Rebound damping tends to become stron-
ger and the front fork may sink deeply over a
series of gaps.
2. Use of stiff spring
• Change the rebound damping force.
Turn in one or two clicks.
• Change the compression damping force.
Turn out one or two clicks.
TIP
Generally a stiff spring gives a stiff riding feel-
ing. Rebound damping tends to become weak-
er, resulting in lack of a sense of contact with
the road surface or in a vibrating handlebar.
EAS1SL1372FRONT FORK SETTING PARTS
• Front fork spring “1”
*Except for USA and CAN
TIP
The I.D. mark (slits) “a” is proved on the end of
the spring.
EAS1SL1373REAR SUSPENSION SETTING
The rear shock absorber setting should be
made depending on the rider's feeling of an ac
-
tual run and the circuit conditions.
The rear suspension setting includes the fol-
lowing two factors:
1. Setting of spring preload
• Change the set length of the spring.
• Change the spring.
2. Setting of damping force
• Change the rebound damping force.
• Change the compression damping force.
EAS1SL1374CHOOSING SET LENGTH
1. Place a stand or a block under the engine to
put the rear wheel above the floor, and mea
-
sure the length “a” between the rear wheel
axle center and the rear fender holding bolt.
Type
Spring
rate
N/mm
Part number
I.D.
Mark
(slits)
SOFT3.91SL-23141-20|-||
4.61SL-23141-30|-|||
STD*4.71SL-23141-10—
1SL-23141-40|-||||
4.81SL-23141-50|-|||||
STD4.91SL-23141-00—
1SL-23141-60||-||
STIFF5.01SL-23141-70||-|||
a
1

CHASSIS
10-6
EAS1SL1377SUSPENSION SETTING (FRONT FORK)
TIP
• If any of the following symptoms is experienced with the standard position as the base, make reset-
ting by reference to the adjustment procedure given in the same chart.
• Before any change, set the rear shock absorber sunken length to the standard figure 90–100 mm
(3.5–3.9 in).
Symptom
Section
CheckAdjustJumpLarge
gapMedi-
um
gapSmall
gap
Stiff over entire
range
Compression
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Oil amountDecrease oil amount by about
5–10 cm3 (0.2–0.3 US oz, 0.2–
0.4 Imp.oz).
SpringReplace with soft spring.
Unsmooth
movement over
entire range
Outer tube
Inner tube
Check for any bends, dents,
other noticeable scars, etc. If
any, replace affected parts.
Slide metalReplace with a new one for ex-
tended use.
Piston metalReplace with a new one for ex-
tended use.
Lower bracket
tightening
torqueRetighten to specified torque.
Poor initial
movement
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Oil sealsApply grease in oil seal wall.
Soft over entire
range, bottom
-
ing out
Compression
damping forceTurn adjuster clockwise (about
2 clicks) to increase damping.
Oil amountIncrease oil amount by about
5–10 cm3 (0.2–0.3 US oz, 0.2–
0.4 Imp.oz).
SpringReplace with stiff spring.
Stiff toward
stroke endOil amountDecrease oil amount by about
5 cm3 (0.2 US oz, 0.2 Imp.oz).
Soft toward
stroke end, bot
-
toming out
Oil amount
Increase oil amount by about 5
cm3 (0.2 US oz, 0.2 Imp.oz).
Stiff initial
movementCompression
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.

CHASSIS
10-7
EAS1SL1378SUSPENSION SETTING (REAR SHOCK ABSORBER)
TIP
• If any of the following symptoms is experienced with the standard position as the base, make reset-
ting by reference to the adjustment procedure given in the same chart.
• Adjust the rebound damping in 2-click increments or decrements.
• Adjust the low compression damping in 1-click increments or decrements.
• Adjust the high compression damping in 1/6 turn increments or decrements.
Low front, tend-
ing to lower
front posture
Compression
damping forceTurn adjuster clockwise (about
2 clicks) to increase damping.
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Balance with
rear endSet sunken length for 95–100
mm (3.7–3.9 in) when one
passenger is astride seat (low
-
er rear posture).
Oil amountIncrease oil amount by about 5
cm3 (0.2 US oz, 0.2 Imp.oz).
”Obtrusive”
front, tending to
upper front pos
-
ture
Compression
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Balance with
rear endSet sunken length for 90–95
mm (3.5–3.7 in) when one
passenger is astride seat (up
-
per rear posture).
SpringReplace with soft spring.
Oil amountDecrease oil amount by about
5–10 cm3 (0.2–0.3 US oz, 0.2–
0.4 Imp.oz).
Symptom
Section
CheckAdjustJumpLarge
gapMedi-
um
gapSmall
gap
Stiff, tending to
sink
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Spring set
lengthSet sunken length for 90–100
mm (3.5–3.9 in) when one
passenger is astride seat.
Spongy and un-
stable
Rebound
damping forceTurn adjuster clockwise (about
2 clicks) to increase damping.
Low compres-
sion damping
Turn adjuster clockwise (about
1 click) to increase damping.
SpringReplace with stiff spring.
SymptomSection
Check Adjust
JumpLarge
gapMedi-
um
gapSmall
gap