Valve Seat Width - Honda GX690 Workshop Manual

CYLINDER SLEEVE I.D.
Measure and record the cylinder I.D. at three levels in
both the "X" axis (perpendicular to crankshaft) and the
"Y" axis (parallel to crankshaft). Take the maximum
reading to determine cylinder wear and taper.
STANDARD: 78.000 – 78.015 mm
(3.0709 – 3.0715 in)
SERVICE LIMIT: 78.150 mm (3.0768 in)
If the measurement is more than the service limit,
replace the cylinder (page 14-5).

VALVE SEAT WIDTH

Remove the carbon deposits from the combustion
chamber (page 3-10).
Inspect each valve face for irregularities.
If necessary, replace the valve (page 14-5).
Apply a light coat of Prussian Blue or erasable felt-
tipped marker ink to the each valve seat.
Using a valve lapper, insert the valve, and snap it
closed against its seat several times. Be sure the valve
does not rotate on the seat.The transferred marking
compound will show any area of the valve face that is
not concentric.
Measure the valve seat width of the cylinder.
STANDARD: 1.0 – 1.2 mm (0.04 – 0.05 in)
SERVICE LIMIT: 2.1 mm (0.08 in)
If the measurement is more than the service limit,
recondition the valve seat (page 14-13).
Check whether the valve seat contact area of the valve
is too high.
If the valve seat is too high, recondition the valve seat
(page 14-13).
VALVE GUIDE I.D.
Ream the valve guide (1) to remove any carbon
deposits before measuring.
TOOL:
Valve guide reamer 5.510 mm (2) 07984-2000001
Turn the special tool (Valve guide reamer) clockwise,
never counterclockwise.
Continue to rotate the special tool while removing it
from the valve guide.
X
BOTTOM
Y
MIDDLE
TOP
VALVE SEAT
WIDTH
(2)
(1)
CYLINDER
(1)
CONTACT
TOO HIGH
14-7