Valve Spring - HYOSUNG 2010 ST7 Service Manual

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.
Valve spring free length
Inner
Outer
Venier calipers : 09900-20101
Valve spring tension
Inner
Outer
CYLINDER DISTORTION
Check the gasketed surface of the cylinder for distor-
tion with a straightedge and thickness gauge, taking a
clearance reading at several places as indicated.
I f t h e l a r g e s t r e a d i n g a t a n y p o s i t i o n o f t h e
straightedge exceeds the limit, replace the cylin-
der.
Cylinder distortion
Thickness gauge : 09900-20806
CYLINDER BORE
Measure the cylinder bore diameter at six place. If any
one of the measurements exceeds the limit, overhaul
the cylinder and replace the piston with an oversize, or
replace the cylinder.
Standard
Cylinder bore 81.500~81.515 mm
(3.2087~3.2093 in)
Cylinder gauge set : 09900-20508
Service limit
36.8 mm (1.45 in)
39.8 mm (1.57 in)
Standard
4.2 ~ 4.8 kgf
(9.3 ~ 10.6 lbs)
at length 29.9 mm (1.18 in)
17.0 ~ 19.6 kgf
(37.5 ~ 43.2 lbs)
at length 33.4 mm (1.32 in)
Service limit
0.05 mm (0.002 in)
Service limit
81.575 mm
(3.2116 in)
ENGINE 3-26