YAMAHA YZ450F 2015 Owners Manual

CRANKCASE
5-66
2. Check:
• Crankcase
Crack/damage  Replace.
• Oil delivery passages
Obstruction  Blow out with compressed
air.
EAS1SL5283ASSEMBLING THE CRANKCASE
1. Install:
• Bearing cover plate
TIP
• Install the bearing by pressing its outer race
parallel.
• To prevent the bearing cover plate screw
(crankshaft) “1” from becoming loose, crimp
the screw head periphery “a” into the concave
“b” using a punch etc. In so doing, take care
not to damage the screwdriver receiving hole
in the screw.
2. Apply:
• Sealant
(to the crankcase mating surface)3. Install:
• Dowel pin “1”
• Crankcase “2”
(to the left crankcase)
TIP
• Apply the lithium-soap-based grease on the
O-ring.
• Fit the right crankcase onto the left crankcase.
Tap lightly on the case with soft hammer.
• When installing the crankcase, the connecting
rod should be positioned at top dead center
(TDC).
• Tighten the bolts in a crisscross pattern in two
(2) stages, with 1/4 turn each. Bearing cover plate
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
LOCTITE®
Bearing cover plate (crankshaft)
18 Nm (1.8 m·kgf, 13 ft·lbf)
Three Bond No.1215®
90890-85505
T R..
a
b
1
1
Crankcase bolt
12 Nm (1.2 m·kgf, 8.7 ft·lbf)
3. 45 mm (1.77 in)
4. 65 mm (2.56 in)
5. 75 mm (2.95 in)
T R..
5
3
5
3
3 3 45 4
3
1
12

CRANKSHAFT ASSEMBLY AND BALANCER SHAFT
5-67
EAS1SL5284
CRANKSHAFT ASSEMBLY AND BALANCER SHAFT
Removing the crankshaft assembly and balancer shaft
Order Part name Q’ty Remarks
CrankcaseSeparate.
Refer to “CRANKCASE” on page 5-62.
Transmission Refer to “TRANSMISSION” on page 5-70.
1 Balancer shaft 1
2 Crankshaft assembly 1
For installation, reverse the removal proce-
dure.
1
2

CRANKSHAFT ASSEMBLY AND BALANCER SHAFT
5-68
EAS1SL5285REMOVING THE BALANCER SHAFT
1. Remove:
• Balancer shaft “1”
TIP
Remove the balancer shaft with its flat side “a”
facing the crankshaft.
EAS1SL5286REMOVING THE CRANKSHAFT ASSEMBLY
1. Remove:
• Crankshaft assembly “1”
TIP
Remove the crankshaft assembly by using the
crankcase separating tool “2”.
EAS1SL5287
CHECKING THE CRANKSHAFT ASSEMBLY
1. Measure:
• Crankshaft runout
Out of specification  Replace the crank-
shaft, bearing or both.
TIP
Turn the crankshaft slowly.
2. Measure:
• Big end side clearance D “a”
Out of specification  Replace the big end
bearing, crankshaft pin, or connecting rod.
3. Measure:
• Crankshaft width A “a”
Out of specification  Replace the crank-
shaft. Crankcase separating tool
90890-04152
YU-A9642
1
a
2
1
Runout limit C
0.030 mm (0.0012 in)
Big end side clearance D
0.150–0.450 mm (0.0059–0.0177
in)
Width A
61.95–62.00 mm (2.439–2.441 in)

CRANKSHAFT ASSEMBLY AND BALANCER SHAFT
5-69
4. Check:
• Crankshaft sprocket “1”
Damage  Replace the crankshaft.
5. Check:
• Crankshaft journal oil passage
Obstruction  Blow out with compressed
air.
EAS1SL5288INSTALLING THE CRANKSHAFT ASSEM-
BLY
1. Install:
• Crankshaft assembly
TIP
Install the crankshaft assembly with the crank-
shaft installer pot “1”, crankshaft installer bolt
“2”, adapter (M12) “3” and spacer “4”.
ECA13970
NOTICE
• To avoid scratching the crankshaft and to
ease the installation procedure, lubricate
the oil seal lips with lithium-soap-based
grease.
• In order to prevent the crankshaft seizure,
apply molybdenum disulfide grease.
TIP
Hold the connecting rod at top dead center
(TDC) with one hand while turning the nut of the
crankshaft installer bolt with the other. Turn the
crankshaft installer bolt until the crankshaft as-
sembly bottoms against the bearing.
Crankshaft installer pot
90890-01274
Installing pot
YU-90058
Crankshaft installer bolt
90890-01275
Bolts
YU-90060
Adapter (M12)
90890-01278
Adapter #3
YU-90063
Spacer (crankshaft installer)
90890-04081
Pot spacer
YM-91044
1

TRANSMISSION
5-70
EAS1SL5289
TRANSMISSION
Removing the transmission, shift drum assembly, and shift forks
Order Part name Q’ty Remarks
Engine Refer to “ENGINE REMOVAL” on page 5-1.
CrankcaseSeparate.
Refer to “CRANKCASE” on page 5-62.
1 Main axle 1
2 Drive axle 1
3 Long shift fork guide bar 1
4 Short shift fork guide bar 1
5Spring 4
6 Shift cam 1
7 Shift fork 3 (R) 1
8 Shift fork 2 (C) 1
9 Shift fork 1 (L) 1
10 Collars 1
For installation, reverse the removal proce-
dure.
2
10
1
53
4 578
69
M
M
M
M
M
EE
E
E
LS
New

TRANSMISSION
5-71
EAS1SL5290REMOVING THE TRANSMISSION
1. Remove:
• Long shift fork guide bar “1”
• Short shift fork guide bar “2”
• Shift cam “3”
• Shift fork 3 “4”
• Shift fork 2 “5”
• Shift fork 1 “6”
• Main axle “7”
• Drive axle “8”
• Collar “9”
TIP
• Remove assembly with the collar “9” installed
to the crankcase.
• Make a note of the position of each part. Pay
particular attention to the location and direc-
tion of shift forks.
• Remove the main axle and the drive axle all
together by tapping the drive axle lightly with
a soft hammer.
EAS1SL5291
CHECKING THE SHIFT FORKS
1. Check:
• Shift fork cam follower “1”
• Shift fork pawl “2”
Bends/damage/scoring/wear  Replace the
shift fork.
2. Check:
• Shift fork guide bar
Roll the shift fork guide bar on a flat surface.
Bends  Replace.
EWA12840
WARNING
Do not attempt to straighten a bent shift fork
guide bar.
3. Check:
• Shift fork movement
(along the shift fork guide bar)
Rough movement  Replace the shift forks
and shift fork guide bar as a set.
1
4
62
5
3
8
7
9

TRANSMISSION
5-72
EAS1SL5292CHECKING THE SHIFT DRUM ASSEMBLY
1. Check:
• Shift drum groove
Damage/scratches/wear  Replace the
shift drum assembly.
• Shift drum segment “1”
Damage/wear  Replace the shift drum as-
sembly.
EAS1SL5293CHECKING THE TRANSMISSION
1. Measure:
• Main axle runout
(with a centering device and dial gauge “1”)
Out of specification  Replace the main ax-
le.
2. Measure:
• Drive axle runout
(with a centering device and dial gauge “1”)
Out of specification  Replace the drive ax-
le.3. Check:
• Transmission gears
Blue discoloration/pitting/wear  Replace
the defective gear (s).
• Transmission gear dogs
Cracks/damage/rounded edges  Replace
the defective gear (s).
4. Check:
• Transmission gear movement
Rough movement  Replace the defective
gear (s).
EAS1SL5294INSTALLING THE TRANSMISSION
1. Install:
• 5th pinion gear (21T) “1”
• 3rd pinion gear (20T) “2”
• Collar “3”
• 4th pinion gear (22T) “4”
• 2nd pinion gear (15T) “5”
(to the main axle “6”)
TIP
Before installation, apply molybdenum disulfide
oil to the inner and end surface of the idler gear
and to the inner surface of the sliding gear, then
install. Main axle runout limit
0.08 mm (0.0032 in)
Drive axle runout limit
0.08 mm (0.0032 in)
34
2
1
6
5
M

TRANSMISSION
5-73
2. Install:
• Collar “1”
• 2nd wheel gear (23T) “2”
• 4th wheel gear (24T) “3”
• 3rd wheel gear (26T) “4”
• 5th wheel gear (20T) “5”
• Collar “6”
• 1st wheel gear (27T) “7”
• O-rings “8”
(to the drive axle “9”)
TIP
• Before installation, apply molybdenum disul-
fide oil to the inner and end surface of the idler
gear and to the inner surface of the sliding
gear, then install.
• Apply the lithium-soap-based grease on the
O-ring.
3. Install:
• Washer “1”
• Circlip “2”
TIP
• Be sure the circlip sharp-edged corner “a” is
positioned opposite side to the washer and
gear “b”.
• Install the circlip with its ends “c” settled even-
ly on the spline crests.4. Install:
• Collar “1”
TIP
• Apply the lithium soap base grease on the oil
seal lip.
• When installing the collar into the crankcase,
pay careful attention to the crankcase oil seal
lip.
5. Install:
• Main axle “1”
• Drive axle “2”
TIP
• Install to the left crankcase simultaneously.
• Apply engine oil to the main axle and the drive
axle bearing.
New
298
3
4
5
6
7
New
M
LS
1
New
21
2
ab
cc
1
2
EE

TRANSMISSION
5-74
6. Install:
• Shift fork 1 (L) “1”
• Shift fork 2 (C) “2”
• Shift fork 3 (R) “3”
• Shift cam “4”
(to the main axle and the drive axle)
TIP
• Apply engine oil to the shift fork grooves.
• Apply engine oil to the shift cam groove and
the bearing contact surface.
• Mesh the shift fork 1 (L) with the 4th wheel
gear “5” and 3 (R) with the 5th wheel gear “7”
on the drive axle.
• Mesh the shift fork 2 (C) with the 3rd pinion
gear “6” on the main axle.7. Install:
• Long shift fork guide bar “1”
• Short shift fork guide bar “2”
• Spring “3”
TIP
• Screw the spring into the shift fork guide bar
lightly beforehand.
• Apply the engine oil on the shift fork guide
bars.
8. Check:
• Operation of shift cam and shift fork
• Transmission operation
Unsmooth operation  Repair.
3
12
EE
E
2 13
E

TRANSMISSION
5-75