Checking The Cylinder Head - Yamaha YFM45FAR Service Manual

CYLINDER HEAD

CHECKING THE CYLINDER HEAD

1.Eliminate:
Carbon deposits (from the combustion
G
chambers)
Use a rounded scraper.
NOTE:
Do not use a sharp instrument to avoid
damaging or scratching:
Spark plug threads
G
Valve seats
G
2.Check:
Cylinder head
G
Scratches/damage → Replace.
Cylinder head water jacket
G
Mineral deposits/rust → Eliminate.
3.Measure:
Cylinder head warpage
G
Out of specification → Resurface.
Cylinder head warpage:
Less than 0.03 mm (0.0012 in)
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Measurement and resurfacing steps:
G
Place a straightedge and a feeler gauge
across the cylinder head.
G
Use a feeler gauge to measure the warpage.
G
If the warpage is out of specification,
resurface the cylinder head.
G
Place a 400 ~ 600 grit wet sandpaper on the
surface plate, and resurface the head using
a figure-eight sanding pattern.
NOTE:
To ensure an even surface rotate the cylinder
head several times.
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ENG