18
(D Compression gauge
3. MAINTENAt'jCE OPERATIONS
14. COMPRESSION PRESSURE
CHECK
. 1. Remove the spark plugs.
2. Insert the end of the compression gauge
into the spark plug hole.
3. Set both the throttle and choke to full
open position and kick the kick starter .
Standard compression pressure:
12 kg /cm
2
(170. 67 psi)
Note:
. Fully open the throttle and choke so that
the true compression pressure will be in-
dicated on the gauge.
· Continue the kicking until the compression
reading
is at maximum because the reading
will increase with each kicking .
. To obtain the true pressure reading, per-
form the measurement after warming up
the engine.
(Low compression pressure)
W hen the compression pressure is below 10
kg/cm
2
(142. 23 psi), the probab le causes are
leaks around the valves and piston rings, or
from the head and cylinder gaskets.
Adjust the valve tappet clearances, or disas-
semble the engine and inspect the piston rings
and gaskets.
(High compression pressure)
When the pressure is greater than 12 kg/cm
2
(170. 67 psi), the probable cause is excessive
carbon deposits on the combustion chamber,
piston head and the valves. Disassemble the
head and cylinder, to remove the carbon .
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