Compression Pressure

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Compression Pressure

Ransomes Twenty Four

In comparison to my Suffolk 43DL which is a solid turn over the above was relatively easy. I took the precaution of doing some compression checks please see attached photos. The higher pressure was after i squirted some oil in the cylinder before the reading.  I used a a drill to rotate the engine.

What is an acceptable pressure for these engines?  Engine data (acceptable wear limits etc) appears scarce.






Thanks for looking

wristpin's picture
I’ve never bothered too much

I’ve never bothered too much about single pot small engine compression figures and as far as I know neither Suffolk nor Villiers ever issued figures. There’s a lot more to be learnt from a leakdown test particularly on engines with automatic compression release  - most other than SIF and Villiers. 

To get a truer reading you

To get a truer reading you need to open throttle fully, also try same with a hot/cold  engine. If no pressure difference on a low figure to start with, it's often a poorly seating valve, generally the exhaust one.

Rule of thumb is compression

Rule of thumb is compression ratio X 14.7 (atmospheric pressure in PSI)

In practice gauge reading will be slightly less, depending on volumetric efficiency of the engine, it gives an idea.

Low compression side valve

Low compression side valve engines such as these will be quite low anyway, also try testing dry against another go with oil down the bore.