- 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