HYOSUNG RX 125 -, Service Manual, Page: 31 / 175

3-1 ENGINE
CAUTION
COMPRESSION PRESSURE
AND OIL PRESSURE
COMEPRESSION PRESSURE
OIL PRESSURE
Before inspecting for compression pressure,
make sure that the cylinder head nuts and bolts
are tightened to specified torque values and
valves are properly adjusted.
Have the engine warmed up by idling before
testing it.
Compression gauae : 09915-64510
● Remove spark plug.
● Fit the compression gauge to the plug hole, taking care
to make the connection absolutely tight.
● Twist the throttle grip into wide-open position.
● Crank the engine several times with the starter motor or
kick starter, and read the highest gauge indication as the
compression of the cylinder.
Install the oil pressure gauge in the position shown
in the illustration.
Warm up the engine as follows.
● Summer approx. 10 min. at 2,000 rpm.
● Winter approx. 20 min. at 2,000 rpm.
After the warming up operation, increase the
engine speed to 3,000 rpm, and read the oil pres-
sure gauge.
It the oil pressure is lower or higher than the speci-
fications, several causes may be considered.
● Low oil pressure is usually the result of a
clogged oil damaged oil seal, a defective oil
pump or a combination of these items, filter, oil
leakage from the oil passage, (damaged oil seal,
a defective oil pump or a combination of these
items.)
● High oil pressure is usually caused by a engine
oil which is too heavy a weight, a clogged oil
passage, improper installation of the oil filter or
a combination of these items.
A low compression pressure may indicate any of
the following malfunction :
● Excessively worn cylinder wall.
● Worn piston or piston rings.
● Piston rings stuck in the grooves.
● Poor sealing contact of valves.
● Defective cylinder head gasket
When the compression pressure noted is down to or
below the limit indicated above, the engine must be
disassembled, inspected and repaired as required to
overhaul the engine, with these five abnormality in mind.
Compression pressure
15.6 kg/㎠ (500 rpm)
8 kg/㎠
Compression pressure
(Standard)
Compression pressure
(Limit)
Oil pressure
0.4 ~ 0.6 kg/㎠
(at 60℃ ∙3,000 rpm)
Oil pressure
NOTE:
Engline oil must be warmed up to 60℃ (140℉)
when checking the oil pressure.
Oil pressure gauge : 09915-74510