Compression Pressure - HYOSUNG Aquila 250 Service Manual

COMPRESSION PRESSURE

The compression of a cylinder is a good indicator of its
internal condition.
The decision to overhaul the cylinder is often based on
the results of a compression test. Periodic maintenance
records kept at your dealership should include compres-
sion reading for each maintenance service.
Compression pressure
Standard
Service limit
Low compression pressure can indicate any of the fol-
lowing conditions :
● Excessively worn cylinder wall
● Worn-down piston or piston rings
● Piston rings stuck in grooves
● Poor seating of valves
● Ruptured or otherwise defective cylinder head gasket
◉ COMPRESSION TEST PROCEDURE
NOTE:
� Before testing the engine for compression pres-
sure, make sure that the cylinder head bolts are
tightened to the specified torque values and
valves are properly adjusted.
� Have the engine warmed up by idling before testing.
� Be sure that the battery used is in fully-charged
condition.
Remove the parts concerned and test the compression
pressure in the following manner.
● Loosen the oil cooler mounting bolts from the frame.
● Remove all the spark plug.
● Fit the compression gauge in one of the plug holes,
while taking care that the connection is tight.
● Keep the throttle grip in full-open position.
● Crank the engine a few seconds with the starter, and
record the maximum gauge reading as the compres-
sion of that cylinder.
Compression gauge : 09915 - 64510
2
14~16 kg/cm (at 600 rpm)
2
12 kg/cm (at 600 rpm)
PERIODIC MAINTENANCE 2-20