P25 Series of Engines
18
Compression testing
To perform a compression test:
NOTE:
If the engine will run, start the engine and let
it warm up first for a better reading.
1.
Disconnect the high-tension lead from the spark
plug and ground it well away from the spark plug
hole.
2.
Remove the spark plug using a 5/8” spark plug
socket.
3.
Pull the starter rope several times to purge any fuel
or oil from the combustion chamber.
NOTE:
Air compresses readily, liquid does not. Liq-
uid in the combustion chamber will result in
an artificially high compression reading.
4.
Install a compression gauge in the spark plug hole.
5.
Confirm that the gauge is “zeroed”, then pull the
starter rope repeatedly, until the needle on the gauge stops rising. See Figure 3.1.
6.
Read the gauge.
NOTE:
When checking compression on small displacement engines, use a compression gauge set with the
shortest available (or no) hose.
Interpreting compression readings:
Readings in psi
Possible causes
<90
(6.2 Bar)
Worn rings and/or a scored cyl-
inder.
90 - 145
(6.2 - 10 Bar)
Normal readings
>145
(>10 Bar)
Hydraulic lock
Figure 3.1
Gauge is zeroed
For Parts Call 606-678-9623 or 606-561-4983
www.mymowerparts.com
Summary of Contents for 25cc
Page 2: ...For Parts Call 606 678 9623 or 606 561 4983 www mymowerparts com...
Page 14: ...P25 Series of engines 10 For Parts Call 606 678 9623 or 606 561 4983 www mymowerparts com...
Page 28: ...P25 Series of Engines 24 For Parts Call 606 678 9623 or 606 561 4983 www mymowerparts com...
Page 62: ...P25 Series of Engines 58 For Parts Call 606 678 9623 or 606 561 4983 www mymowerparts com...
Page 63: ...For Parts Call 606 678 9623 or 606 561 4983 www mymowerparts com...
