Honda SH125 Manual page 170

CYLINDER HEADNALVES
VALVE SPRING
Check the valve springs for fatigue or damage.
Measure the valve spring free length.
SERVICE LIMIT: IN/EX: 34.4 mm (1.35 in)
VALVENALVE GUIDE
Check that the valve moves smoothly in the guide.
Check the valves for bending, burning or abnormal
wear.
Measure each valve stem O.D. and record
it.
SERVICE LIMIT: IN/EX: 4.90 mm (0.193 in)
Ream the guides to remove any carbon build-up
before measuring the guide.
Insert the reamer from the combustion chamber
side of the head and always rotate the reamer clock-
wise.
TOOL:
Valve guide reamer, 5.0 mm 07984-MA60001
Measure each valve guide I.D. and record it.
SERVICE LIMIT: IN/EX: 5.03 mm (0.198 in)
Subtract each valve stem O.D. from the correspond-
ing guide I.D. to obtain the stem-to-guide clearance.
SERVICE LIMITS: IN: 0.08 mm (0.003 in)
EX: 0.10 mm (0.004 in)
lnspect and reface
If the stem-to-guide clearance exceeds the service
the valveseats
limit, determine if
a
new guide with standard
whenever the valve
dimensions would bring the clearance within toler-
guidesarereplaced
ance. If so, replace any guides as necessary and
If the stem-to-guide clearance exceeds the service
limit with a new guide, also replace the valve.
(page
8-76). ream to fit.