KITPLANES Firewall Forward: Spark Plug Maintenance


CFR 43.3 describes, in a long list, the maintenance items a pilot/owner can legally do. In this video, KITPLANES editor at large Paul Dye runs through how to remove, inspect, clean and gap spark plugs. Learning to do this can not only save you money, but reduce the frustration of suffering a bad runup because of a fouled plug.

Paul Dye
Paul Dye, KITPLANES® Editor at Large, retired as a Lead Flight Director for NASA’s Human Space Flight program, with 40 years of aerospace experience on everything from Cubs to the Space Shuttle. An avid homebuilder, he began flying and working on airplanes as a teen, and has experience with a wide range of construction techniques and materials. He flies an RV-8 that he built, an RV-3 that he built with his pilot wife, as well as a Dream Tundra they completed. Currently, they are building a Xenos motorglider. A commercially licensed pilot, he has logged over 5000 hours in many different types of aircraft and is an A&P, EAA Tech Counselor and Flight Advisor, as well as a former member of the Homebuilder’s Council. He consults and collaborates in aerospace operations and flight-testing projects across the country.

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  1. Please use the Champion or Tempest Manuals to do this maintenance, not this video.
    Besides, using the manual is required in the Regulations.

  2. Several errors in this video. Using a sandblaster is not recommended for aviation plugs, the blast media may wind up in your engine. If you use a crows foot as he mentioned , you may overtorque if it is not positioned correctly, 90 degrees to the wrench. I wouldn’t use a wire wheel on a plug either, it removes plating. Don’t use a Thread-chaser as you may pull out or damage the helicoil, and then its cylinder removal time! And as far as putting the plugs in the same hole, they should be rotated for mag polarity, on a 4 cylinder engine diagonally opposite. Its more complicated on a 6 cylinder. So yeah, get the manual so you don’t do some expensive damage to your engine! Check out publications from the plug manufacturers! TC A &P/ IA

    • Hi Tom,
      “Mag polarity” meaning that the 2 mags on an engine can have different polarity?
      That may be a hard one to explain – technically.
      my take
      (besides, I have never seen plug erosion differ from left or right mags)

  3. No, that’s not the idea. The SAME mag fires as Positive and negative, after all, it’s a magneto! Not hard to explain, I’ll quote Champion: “Other conditions that will cause excessive electrode erosion is constant polarity and high capacitance. Constant polarity occurs with even-numbered cylinder magnetos. One plug fires with positive polarity causing excessive ground electrode wear, while the next plug fires negatively causing excessive center electrode wear”. Many owners extend plug life in this manner, others don’t bother and just replace when some wear shows. But looking at what platinum or iridium plugs go for, it’s worth it to extend their life as well as massive plugs. Look up Champion’s diagram for 6 cylinder engines. Rotating plugs properly can extend their life. TC