Cylinder Head - Yamaha YZ250F(P)/LC Owner's Service Manual

CYLINDER HEAD

INSPECTION
Cylinder head
1. Eliminate:
Carbon deposits (from the combustion
G
chambers)
Use a rounded scraper.
NOTE:
Do not use a sharp instrument to avoid dam-
aging or scratching:
Spark plug threads
G
Valve seats
G
2. Inspect:
Cylinder head
G
Scratches/damage → Replace.
3. Measure:
Cylinder head warpage
G
Out of specification → Resurface.
Cylinder head warpage:
Less than 0.05 mm (0.002 in)
Warpage measurement and resurface-
ment steps:
Place a straightedge and a feeler gauge
G
across the cylinder head.
Use a feeler gauge to measure the
G
warpage.
If the warpage is out of specification,
G
resurface the cylinder head.
Place a 400 ~ 600 grit wet sandpaper on
G
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.
4 - 30
ENG