Yamaha WR250FM 2021, Owner'S Service Manual

Page: 268 / 404

CRANKCASE
5-68
EAM30147
DISASSEMBLING THE CRANKCASE
1. Separate:
•
Right crankcase
• Left crankcase
a. Remove the crankcase bolts.
TIP
Loosen each bolt 1/4 of a turn at a time and after
all the bolts are loosened, remove them.
b. Remove the right crankcase “1”.
TIP
•
Place the crankcase with its left side down-
ward, split the crankcase splitting rib “a” while
tap with a soft hammer.
• Lift the right crankcase horizontally while lightly
patting the crankcase splitting rib and the en-
gine mounting boss using a soft hammer, and
leave the crankshaft and the transmission with
the left crankcase.
NOTICE
ECA24690
Use soft hammer to tap on the case half. Tap
only on reinforced portions of case. Do not
tap on gasket mating surface. Work slowly
and carefully. Make sure the case halves
separate evenly. If the cases do not separate,
check for a remaining case bolt or fitting. Do
not force.
c. Remove the dowel pins.
2. Remove:
•
Bearing “1”
TIP
• Remove the bearing from the crankcase by
pressing its inner race.
• Do not use the removed bearing.
EAM30490
CHECKING THE TIMING CHAIN GUIDE
(EXHAUST SIDE)
1. Check:
•
Timing chain
Stiffness

Replace the camshaft sprocket,
timing chain and crankshaft sprocket as a
set.
2. Check:
• Timing chain guide
Damage/wear

Replace.
EAM30150
CHECKING THE CRANKCASE
1. Wash:
• Crankcase
TIP
•
Wash the crankcase in a mild solvent.
• Remove any remaining gasket from the crank-
case mating surface.
2. Check:
• Crankcase
Crack/damage

Replace.
• Oil delivery passages
Obstruction

Blow out with compressed air.
1
a
a