COMPRESSION TEST
The results of a compression check can be useful in determining if an engine is in good operating
condition or if reconditioning is necessary.
To check compression, remove spark plugs, insert com
-
pression gauge
in spark plug hole, set the throttle and choke to the wide open position,
insure that
air intake and exhaust systems are not restricted, and motor the engine using the starting motor. Take
several readings on both cylinders.
A difference in pressure reading between cylinders in excess of
15% or readings below
90
PSI
can indicate the following:
POSSIBLE
CAUSE
A.
Cylinder head gasket blown.
B.
Cylinder head warped or loose.
C.
Piston rings worn
-
blowby occurring.
D. Valves leaking.
E. Excessive combustion deposits.
REMEDY
A.
Remove head, check for flatness, replace gasket,
reinstall head, recheck compression. Locate
cause of initial failure and rectify.
8.
Remove head, check for flatness, (see cylinder
head service). Locate cause
of
initial failure
and rectify.
C.
Recondition engine.
D.
Recondition valves and seats.
E. Remove head and clean combustion deposits from
combustion chamber.
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