HYOSUNG COMET 125 Service Manual page 57

CAMSHAFT
The camshaft should be checked for runout and also for
wear of cams and journals if the engine has been noted
to produce abnormal noise or vibration or a lack of out-
put power. Any of these abnormality could be caused by
a worn camshaft.
CAMSHAFT WEAR
Worn-down cams are often the cause of mistimed valve
operation resulting in reduced output power.
The limit of cam wear is specified for both intake and
exhaust cams in terms of cam height
measured with a micrometer. Replace camshafts if
found it worn down to the limit.
Cam height
Intake cam
Exhaust cam
Micrometer 25~50 mm : 09900-20202
Tappet & shim wear
When measuring the valve clearance, the clearance
should be within the standard range.
Valve clearance
Intake valve
Exhaust valve
Inspect the tappet for wear and scratch.
If modification or scratch is present, replace the tap-
pet.
The shim has various size.
Replace the thin shim to valve clearance is narrow, or
the thick shim to valve clearance is wide as that shim
thickness was installed with standard at present.
(Refer to page 7-33 34)
SHIM KIND
There are 41 kinds of shim which thickness is increased
by each 0.025 mm from 1.20 mm to 2.20 mm.
, which is to be
Service limit
34.170 mm (1.345 in)
34.120 mm (1.343 in)
Standard(When cold)
0.1~0.2 mm
(0.004~0.008 in)
0.2~0.3 mm
(0.008~0.012 in)
(T.D.C)
(B.T.D.C)
Intake open
Exhaust close
17 45
48
14
(A.B.D.C)
Intake close
(B.D.C)
Valve timing diagram
ENGINE 3-20
(A.T.D.C)
(B.B.D.C)
Exhaust open