Yamaha 40V, Service Manual

Page: 98 / 224

5-23
POWR
E
CYLINDER HEAD, THERMOSTAT AND EXHAUST
COVER
SERVICE POINTS
Cylinder head inspection
1. Inspect:
●
Water jacket
Material deposit/Corrosion
→
Clean.
●
Cylinder inner surface
Score marks
→
Clean.
Use #600 ~ 800 grit wet sandpaper.
CAUTION:
Do not scratch the fitting surfaces of the
cylinder and cylinder cover.
2. Measure:
●
Cylinder head warpage
Use a straightedge and thickness
gauge.
Out of specification
→
Resurface or
replace.
Warpage limit:
0.1 mm (0.004 in)
Resurfacing steps:
●
Place a 400 ~ 600 grit wet sandpaper
on the surface plate.
●
Resurface the head using a figure-
eight sanding pattern.
NOTE:
Rotate the head several times to avoid
removing too much material from one
side.