What can cause compression loss?

[Erude73]

aside from bad rings or scored up cylinders, or headgasket,is there anything else that can cause low compression on a 2 stroke? i have a 4 and 15hp for a friend and both on my compression gauge read around 20-30 lbs.

 

[Silvertip]

1) bad compression gauge, 2) incorrect compression test procedure, 3) compression gauge not sealing in the plug hole. All three have nothing to do with the condition of the engine. I highly doubt all cylinders are bad -- and bad in the same range. You mentioned "bad rings" but "stuck rings" due to carbon deposits can cause low compression. Otherwise you hit the most common issues.

 

[oldboat1]

If the numbers are right, neither one of the motors is running (presumably). Might try a different screw in gauge -- test with both plugs out; pull it over repeatedly until the needle stops rising (maybe four or five pulls).

 

[jimmbo]

Warped head and damaged piston crown are two more causes. Poorly done sparkplug thread repair is another

 

[boobie]

Do the motors run ??

 

[Erude73]

found it, was a cracked skirt thanks

 

[boobie]

On both motors ??