[Public-List] atomic 4 compression test

Jason S mpcylinderheads at gmail.com
Sat Dec 1 10:46:09 PST 2012

Black soot is usually a fuel/carb issue or vacuum leak of some sort. I
would check out Moyer marine website. They have a forum for the A4 that
can't be beat. Also great specs such as stock compression and such. Good
On Dec 1, 2012 12:06 PM, "Sandi & Mark Bisset" <sandimark at rogers.com> wrote:

> We are currently rebuilding an old Atomic 4 and trying to determine a
> baseline for compression. We were testing the engine when it was cold,
> using a battery, and got results in the 100-110 range. Adding oil increased
> compression to 115-125ish. The plugs are fouling very quickly in regular
> useage (black soot, not oily) and the engine is running rough at times with
> significant vibration. It has been suggested that it needs a ring and/or
> valve job. But the compression seems to be in the specified range.
> Any thoughts would be much appreciated.
> Mark Bisset
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