lug pattern YAMAHA WR 250F 2002 Owners Manual

4 - 31
ENG

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 dam-
aging 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 resurface-
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.