Yamaha WR250F(N) Owner's Service Manual page 448

CRANKCASE AND CRANKSHAFT
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Crankshaft
1. Remove:
Crankshaft 1
Use the crankcase separating tool 2.
Crankcase separating tool:
YU-1135-A/90890-01135
CAUTION:
Do not use a hammer to drive out the
crankshaft.
Crankcase bearing
1. Remove:
Bearing 1
NOTE:
Remove the bearing from the crankcase by
pressing its inner race.
Do not use the removed bearing.
INSPECTION
Timing chain and timing chain guide
1. Inspect:
Timing chain
Cracks/stiff
and camshaft sprocket as a set.
2. Inspect:
Timing chain guide
Wear/damage
Crankcase
1. Inspect:
Contacting surface a
Scratches
Engine mounting boss b, crankcase
Cracks/damage
2. Inspect:
Bearing
Rotate inner race with a finger.
Rough spot/seizure
3. Inspect:
Oil seal
Damage Replace.
ENG
Replace the timing chain
Replace.
Replace.
Replace.
Replace.