View source for EggH6:CompressionCheck

= Compression Check =

* Buy an automotive style compression tester from an auto parts store.
* Run the engine for a minute or two so it is slightly warm and has oil throughout
* Remove all 6 wires from the coils (Be gentle with the locking clips)
* Remove all six coils by loosening bolts until coil pulls off the spark plug
* Remove spark plugs with 5/8 sparkplug socket.  Hold tool straight to prevent braking the plug
* Screw compression tester into one cylinder until seated against the O-ring on tester
* Open the throttle fully
* Stay clear of the propeller and tie the airplane down
* Provide power to the starter switch but leave the ignition off. 
* Press the start switch and watch the needle on the compression tool.  It will stabilize after a few seconds of cranking and not increase any more.  
* Write down this reading.  It will be somewhere between 180 and 230 psi.
* Repeat the test on the rest of the cylinders (Be sure to reset the tool by pressing the button and release previous pressure)
* Below 180 - clean engine with marvel mystery oil in the gas / use auto fuel only for a while
* 180 to 190 is good
* 190 to 210 is great
* 210 to 230 can't get better and be sure to use good quality fuel
* Reinstall spark plugs with a small amount of anti seize on the second and third thread of the plug (stay away from the electrode)
* Tighten new plugs until the built-in crush washer is compressed.  You can feel it compressing.
* Tighten older plugs (washer already compressed, until snug against the block, then 1/8 turn)
* Reinstall coils
* Reinstall coil wires
* Close the throttle
* Record results in the engine logbook