Yamaha SR125 1997, Service Manual

Page: 87 / 243

4-7
CYLINDER HEAD
ENG
NOTE:
NOTE:
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NOTE:
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5. Remove:
Cylinder head
Loosen the nuts in their proper loosening
sequence.
Start by loosening each nut 1 / 2 turn until all
are loose.
YP402000
CYLINDER HEAD INSPECTION
1. Eliminate:
Carbon deposits
(from combustion chambers)
Use a rounded scraper.
Do not use a sharp instrument to avoid
damaging or scratching:
Spark plug threads
Valve seats
2. Inspect:
Cylinder head
Scratches / damage
Replace.
3. Measure:
Cylinder head warpage
Out of specification
Resurface.
Cylinder head warpage:
Less than 0.03 mm
Warpage measurement and resurfacement
steps:
Place a straightedge and a feeler gauge
across the cylinder head.
Measure the warpage.
If the warpage is out of specification, resurface
the cylinder head.
Place a 400 600 grit wet abrasive paper on
the surface plate, and resurface the head us-
ing a figure-eight sanding pattern.
Rotate the cylinder head several times for an
even resurfacement.