Engine Component Inspection And Service - HYOSUNG Aquila 250 Service Manual

ENGINE COMPONENT INSPEC-
TION AND SERVICE
CAUTION
Be sure to identify each removed part as to its loca-
tion, and lay the parts out in groups designated as
"Front cylinder" , "Rear cylinder" , "Exhaust" ,
"Intake" , so that each will be restored to the origi-
nal location during assembly.
◉ CYLINDER HEAD DISTORTION
Decarbonate in combustion chamber.
Check the gasketed surface of the cylinder head for dis-
tortion with a straightedage and thickness gauge, taking
a clearance reading at several places as indicated. If the
largest reading at any position of the straightedge
exceeds the limit, replace the cylinder head.
Cylinder head
distortion
Thickness gauge : 09900-20806
◉ VALVE FACE WEAR
Visually inspect each valve face for wear. Replace any
valve with an abnormally worn face. The thickness of
the valve face decreases as the face wears. Measure
the valve head �. If it is out of specification, replace the
valve with a new one.
Valve face wear
Vernier calipers : 09900-20101
◉ VALVE STEM RUNOUT
Check the valve stem for abnormal wear or bend.
Place the valve on V-blocks and measure runout.
If the service limit is exceeded or abnormal condition
exists, replace the valve.
Valve stem runout
Dial gauge : 09900-20606
Magnetic stand : 09900-20701
V-block : 09900-21304
◉ 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.
Service limit
0.05 mm
Service limit
0.5 mm
Service limit
0.05 mm
(T.D.C)
(B.T.D.C)
19
Intake open 32
(A.B.D.C)
Intake close
57
(B.D.C)
Valve timing diagram
ENGINE 3-20
�
(A.T.D.C)
Exhaust close
(B.B.D.C)
38 Exhaust open