Checking The Cylinder Head - Yamaha Raptor 90 YFM90RA 2011 Service Manual

CYLINDER HEAD
EBS00230

CHECKING THE CYLINDER HEAD

1. Eliminate:
• combustion chamber carbon deposits
(with a rounded scraper)
TIP
Do not use a sharp instrument to avoid damag-
ing or scratching:
• spark plug bore threads
• valve seats
2. Check:
• cylinder head
Damage/scratches → Replace.
3. Measure:
• cylinder head warpage
Out of specification → Resurface the cylin-
der head.
Maximum cylinder head warpage
0.05 mm (0.002 in)
a. Place a straightedge and a thickness gauge
across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylin-
der head as follows.
d. Place a 400 ~ 600 grit wet sandpaper on
the surface plate and resurface the cylinder
head using a figure-eight sanding pattern.
TIP
To ensure an even surface, rotate the cylinder
head several times.
4 - 8
ENG