HYOSUNG COMET 125 Service Manual page 58

3-21 ENGINE
VALVE HEAD RADIAL RUNOUT
Place a dial gauge as shown and measure valve head
radial runout.
If the service limit is exceeded, replace the valve.
Valve head radial
runout
Dial gauge : 09900-20606
Magnetic stand : 09900-20701
V-block : 09900-21304
VALVE GUIDE-VALVE STEM CLEAR-
ANCE
Measure the clearance in the valve guide-valve stem, by
rigging up the dial gauge as shown. If the clearance
is measured exceeds the limit specified below, then
determine whether the valve or the guide should be
replaced to reduce the clearance to within the standard
range:
Valve guide-valve stem clearance
IN.
EX.
Dial gauge : 09900-20606
Magnetic stand : 09900-20701
VALVE STEM DIAMETER
Measure the valve stem outside diameter.
If the diameter measured exceeds the standard, replace
the valve.
Valve stem diameter
4.475~4.490 mm
IN.
(0.1762~0.1768 in)
4.455~4.470 mm
EX.
(0.1754~0.1760 in)
Micrometer(0~25 mm) : 09900-20201
VALVE SPRING
The force of the coil spring keeps the valve seat tight. A
weakened spring results in reduced engine power out-
put and often accounts for the chattering noise coming
from the valve mechanism.
Check the valve springs for proper strength by measur
ing their free length and also by the force required
to compress them. If the spring length is less than the
service limit or if the force required to compress the
spring does not fall within the specified range, replace
both the inner and outer springs as a set.
Service limit
0.03 mm (0.0012 in)
Standard
0.010~0.037 mm
(0.0004~0.0015 in)
0.030~0.057 mm
(0.0012~0.0022 in)
Standard
3.975~3.990 mm
(0.1565~0.1571 in)
3.955~3.970 mm
(0.1557~0.1563 in)