Yamaha WR250FM Bicycle User Manual


 
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ENG
CYLINDER HEAD
INSPECTION
Cylinder head
1. Eliminate:
Carbon deposits
(from the combustion chambers)
Use a rounded scraper.
N
OTE:
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 resurfacing
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.
N
OTE:
To ensure an even surface rotate the cylin-
der head several times.