lug pattern YAMAHA YZ250LC 2004 Owners Manual

4-21
ENGCYLINDER HEAD, CYLINDER AND PISTON
EC474000
INSPECTION
EC474102
Cylinder head
1. Eliminate:
9Carbon deposits
Use a rounded scraper 1.
NOTE:
Take care to avoid damaging the spark plug
threads. Do not use a sharp instrument. Avoid
scratching the aluminum.
2. Inspect:
9Cylinder head water jacket
Crust of minerals/Rust Remove.
9Cylinder head warpage
Out of specification Re-surface.
Warpage measurement and re-surface-
ment steps:
9Attach a straightedge 1and a thickness
gauge 2on the cylinder head.
9Measure the warpage.
9If the warpage is out of specification, resur-
face the cylinder head.
9Place # 400~600 grit wet sandpaper 3on
the surface plate, and re-surface the head
4using a figure-eight sanding pattern.
NOTE:
Rotate the cylinder head several times to
avoid removing too much material from one
side.
Warpage limit:
0.03 mm(0.0012 in)
3. Remove:
9Piston ring 1
NOTE:
Take care not to scratch the piston or damage
the piston ring by expanding it more than neces-
sary.
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