Yamaha XG250, Service Manual

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CYLINDER HEAD
5-8
2. Check:
●
Cylinder head
Damage/scratches
→
Replace.
3. Measure:
●
Cylinder head warpage
Out of specification
→
Resurface the cylinder
head.
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a. Place a straightedge “1” and a thickness
gauge “2” across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylinder
head as follows.
d. Place a 400
–
600 grit wet sandpaper on the
surface plate and resurface the cylinder head
using a figure-eight sanding pattern.
NOTE:
To ensure an even surface, rotate the cylinder
head several times.
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EAS24180
CHECKING THE TIMING CHAIN GUIDES
The following procedure applies to the camshaft
sprockets and timing chain guides.
1. Check:
●
Timing chain
Damage/stiffness
→
Replace the timing
chain and camshaft sprocket and crankshaft
sprocket as a set.
2. Check:
●
Camshaft sprocket
More than 1/4 tooth wear “a”
→
Replace the
timing chain and camshaft sprocket and
crankshaft sprocket as a set.
3. Check:
●
Timing chain guide (exhaust side)
EAS24190
CHECKING THE TIMING CHAIN
TENSIONERS
1. Check:
●
Timing chain tensioner
Cracks/damage
→
Replace.
2. Check:
●
One-way cam operation
Rough movement
→
Replace the timing
chain tensioner housing.
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a. Lightly press the timing chain tensioner rod
into the timing chain tensioner housing by
hand.
NOTE:
While pressing the timing chain tensioner rod,
wind it clockwise with a thin screwdriver “1” until
it stops.
b. Remove the screwdriver and slowly release
the timing chain tensioner rod.
c. Make sure that the timing chain tensioner rod
comes out of the timing chain tensioner
housing smoothly. If there is rough move-
Warpage limit
0.03 mm (0.0012 in)
1
2
a. 1/4 tooth
b. Correct
1. Timing chain
2. Camshaft sprocket
1
2
a
b