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