Yamaha YZ450F(V) Owner's Service Manual page 302

CYLINDER HEAD
INSPECTION
Cylinder head
1. Eliminate:
• Carbon deposits (from the combustion
chambers)
Use a rounded scraper.
NOTE:
Do not use a sharp instrument to avoid damag-
ing 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 0.05 mm (0.002 in)
Warpage measurement and re-surface-
ment steps:
• Place a straightedge and a feeler gauge
across the cylinder head.
• Use a feeler gauge to measure the
warpage.
• If the warpage is out of specification,
resurface the cylinder head.
• 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 cylin-
der head several times.
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ENG