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Yamaha 2011 WR250FA Owner's Service Manual page 219

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CHECKING THE TIMING CHAIN AND
TIMING CHAIN GUIDE
1. Inspect:
• Timing chain
Cracks/stiff → Replace the timing chain and
camshaft sprocket as a set.
2. Inspect:
• Timing chain guide
Wear/damage → Replace.
CHECKING THE CRANKCASE
1. Inspect:
• Contacting surface "a"
Scratches → Replace.
• Engine mounting boss "b", crankcase
Cracks/damage → Replace.
2. Inspect:
• Bearing
Rotate inner race with a finger.
Rough spot/seizure → Replace.
3. Inspect:
• Oil seal
Damage → Replace.
CRANKCASE AND CRANKSHAFT
CHECKING THE 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
Runout lim-
0.03 mm (0.0012 in)
it:
Small end
0.4–1.0 mm (0.016–
free play:
Side clear-
ance:
(0.0059–0.0177 in)
Crack
55.95–56.00 mm
width:
(2.203–2.205 in)
5-86
Standard
<Limit>
0.05 mm
(0.002 in)
2.0 mm
0.039 in)
(0.08 in)
0.15–0.45 mm
0.50 mm
(0.02 in)

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