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  • This is how we took compression on our Viking 130 aircraft engine. Necessary tools will also include a reliable automotive compression tester with 10mm thread adapter, spark plug socket w/magnet built-in to lift plug from deep well, and inch/lb torque wrench.

    1. Allow engine to reach operating temperature.
    2. Disconnect the electrical connector to each ignition coil, and remove the coils.
    3. Remove the four spark plugs. Ensure debris does not fall into the cylinders. Note: lay out spark plugs and analyze condition.
    4. Attach the compression gauge to the first spark plug hole.
    5. Remove the air filter and ensure the throttle is fully open.
    6. Crank the engine with the starter motor as many as ten revolutions, and measure compression.
    7. Remove compression gauge.
    8. Repeat steps 6 & 7 on the other three cylinders.
    9. Reinstall spark plugs and ignition coils. Note: use aluminum anti seize on the plug threads.
    10. Reconnect the ignition coil electrical connectors.
    11. Log engine hours and findings in maintenance records.

    Compression Pressure should be above 981 kPa (10.00 kgf/cm2, 142.2 psi)



    Maximum Variation between cylinders should be within 196 kPa (2.00 kgf/cm2, 28.4 psi)


    If the compression is not within proper specifications, perform a cylinder leak down test to determine the problem area. Consider the following items:

    Incorrect Valve clearance
    Confirmation of Cam timing
    Damaged or worn Cam Lobes
    Damaged or worn Valves and Seats
    Damaged Cylinder Head gasket
    Damaged or worn Piston Rings
    Damaged or worn Piston and Cylinder bore



  • Well done Loren
  • Loren, thank you very much. This is very helpful.
  • What kind of compression gauge are you using? Mine doesn't reach into the spark plug hole. I need to find an adapter, or fabricate an extension. I have the 180hp engine, so it may be deeper than the 130hp engine.
    • Eric, I have an old compression tester kit that has a 12" hose attached which fits different plug threads. Added a 10mm thread attachment, and it works great.
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