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SECTION 4
TROUBLESHOOTING
Compression Test
3. Crank the engine using the starter motor. Take
To test compression:
several readings for both cylinders.
1, Remove the spark plugs. Install compression tes-
If the difference in pressure between cylinders is
ter in each spark plug hole.
15% or greater, or pressure is less than 90 psig,
2. Set the throttle and choke controls to the wide
check for the conditions below:
open position. Make sure air cleaner and exhaust
system are not restricted.
LOW COMPRESSION
Г
Possible Cause
Solution
1. Blown cylinder head gaskets.
1, Remove cylinder heads, Inspect heads for flatness
(replace heads if necessary), replace gaskets, re-
Install heads, and recheck compression.
Locate
and correct the cause of initial failure.
2. Warped or loose cylinder heads.
2. Remove cylinder heads, check for flatness (replace
heads if necessary). Make sure cylinder head fas-
teners are torqued in the proper sequence to the
proper value.
3. Excessive combustion chamber deposits.
3. Remove cylinder heads and clean deposits from
combustion chamber.
4. Wom piston rings - blowby occurring.
4. Recondition piston rings and cylinder bores.
5. Wom valves.
5. Recondition valves and valve seals.
4.4
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