Yamaha Wr 450 F Owners Manual

4 - 88
ENGENGINE REMOVAL
Drive sprocket
1. Install:
Drive sprocket 1 
Drive chain 2 
NOTE:
Install the drive sprocket together with the
drive chain.
2. Install:
Lock washer 1 
Nut (drive sprocket) 2 
NOTE:
Tighten the nut while applying the rear brake.
New
T R..75 Nm (7.5 m · kg, 54 ft · lb)
3. Bend the lock washer tab to lock the nut.
4. Install:
Chain guide
Chain cover 1 
Screw (chain cover) 2 
5. Install:
O-ring 1 
Dowel pin 2
Oil hose 3
Bolt (oil hose) 4
NOTE:
Apply the lithium soap base...

4 - 89
ENGCRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
Extent of removal:1 Crankcase separation2 Crankshaft removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE SEPARATION
Preparation for removal Engine Refer to “ENGINE REMOVAL” section.
Piston Refer to “CYLINDER AND PISTON” sec-
tion.
Balancer Refer to “BALANCER” section.
Kick axle assembly
Refer to “KICK AXLE AND SHIFT 
SHAFT” section.
Segment
Stator Refer to “AC MAGNETO AND 
STARTER CLUTCH” section.
1 Timing...

4 - 90
ENGCRANKCASE AND CRANKSHAFT
Extent of removal Order Part name Q’ty Remarks
10 Oil strainer 1
11 Oil delivery pipe 2 1
12 Crankshaft 1 Use special tool.
Refer to “REMOVAL POINTS”.
2 

4 - 91
ENGCRANKCASE AND CRANKSHAFT
CRANKCASE BEARING
Extent of removal:1 Crankcase bearing removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE BEARING 
REMOVAL
Preparation for removal Transmission 
Shift cam and shift forkRefer to “TRANSMISSION, SHIFT 
CAM AND SHIFT FORK” section.
1 Oil seal 3
2 Bearing 10 Refer to “REMOVAL POINTS”.
1 

4 - 92
ENGCRANKCASE AND CRANKSHAFT
REMOVAL POINTS
Crankcase
1. Separate:
Crankcase (right)
Crankcase (left)
Separation steps:
Remove the crankcase bolts, hose guide
and clutch cable holder.
NOTE:
Loosen each bolt 1/4 of a turn at a time and
after all the bolts are loosened, remove
them.
Remove the crankcase (right).
NOTE:
Place the crankcase with its left side
downward and split it by inserting a screw-
driver tip into the splitting slit a in the
crankcase.
Lift the crankcase (right) horizontally...

4 - 93
ENGCRANKCASE AND CRANKSHAFT
Crankshaft
1. Remove:
Crankshaft 1 
Use the crankcase separating tool 2.
CAUTION:
Do not use a hammer to drive out the
crankshaft.
Crankshaft bearing
1. Remove:
Bearing 1 
NOTE:
Remove the bearing from the crankcase by
pressing its inner race.
Do not use the removed bearing.
Crankcase separating tool:
YU-1135-A/90890-01135
INSPECTION
Timing chain and timing chain guide
1. Inspect:
Timing chain
Cracks/stiff → Replace the timing chain
and camshaft sprocket as a set....

4 - 94
ENGCRANKCASE AND CRANKSHAFT
EC4N4201
Crankshaft
1. Measure:
Runout limit a 
Small end free play limit b 
Connecting rod big end side clearance
c 
Crank width d 
Out of specification → Replace.
Use the dial gauge and a thickness
gauge.
Dial gauge and stand:
YU-3097/90890-01252
Standard 
Runout 
limit:0.03 mm 
(0.0012 in)0.05 mm 
(0.002 in)
Small end 
free play:0.4 ~ 1.0 mm 
(0.016 ~ 0.039 in)2.0 mm 
(0.08 in)
Side 
clearance:0.15 ~ 0.45 mm 
(0.0059 ~ 0.0177 in)0.50 mm 
(0.02 in)
Crack...

4 - 95
ENGCRANKCASE AND CRANKSHAFT
EC4N5000
ASSEMBLY AND INSTALLATION
Crankshaft bearing
1. Install:
Bearing 
Bearing stopper
Bolt (bearing stopper)
Screw (bearing stopper)
Screw [bearing stopper (crankshaft)] 1 
To crankcase (left and right).
NOTE:
Install the bearing by pressing its outer race
parallel.
To prevent the screw [bearing stopper
(crankshaft)] from becoming loose, crush the
screw head periphery a into the concave b
using a punch etc. In so doing, take care not
to damage the...

4 - 96
ENGCRANKCASE AND CRANKSHAFT
NOTE:
Hold the connecting rod at top dead center
with one hand while turning the nut of the
installing tool with the other. Operate the
installing tool until the crankshaft bottoms
against the bearing.
Before installing the crankshaft, clean the
contacting surface of crankcase.
CAUTION:
Do not use a hammer to drive in the crank-
shaft.
2. Check:
Shifter operation
Transmission operation
Unsmooth operation → Repair.
3. Install:
Oil strainer 1 
Bolt (oil strainer) 2...

4 - 97
ENGCRANKCASE AND CRANKSHAFT
5. Install:
Dowel pin 1 
O-ring 2 
Crankcase (right)
To crankcase (left).
NOTE:
Fit the crankcase (right) onto the crankcase
(left). Tap lightly on the case with soft ham-
mer.
When installing the crankcase, the connect-
ing rod should be positioned at TDC (top
dead center).
New
6. Tighten:
Hose guide 1 
Clutch cable holder 2 
Bolt (clutch cable holder)
Bolt (crankcase)
NOTE:
Tighten the crankcase tightening bolts in
stage, using a crisscross pattern.
7....