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Thread: Well I tried to fly today

  1. #1
    Flyjeep's Avatar
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    Default Well I tried to fly today

    I dragged the plane out and tried to start it and it wasnít firing off so I switched from left mag to both and it fired right up. So I just figured go out run it up and lean it till it cleared. After trying several times left mag just will not clear so back to the hanger.. It drops about 1k rpms it is still running but vary poorly pops and backfires. Iím assuming plugs, it ran perfect last time I flew.
    So now itís time to get sockets and a torque wrench for my hangar so I can at least check my plugs.

  2. #2
    Pacerfgoe's Avatar
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    Default Re: Well I tried to fly today

    Just better to have it happen on the ground rather than in the air....hope it's an easy fix
    Forrest Miller

  3. #3
    Flyjeep's Avatar
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    Default Re: Well I tried to fly today

    Me to ,but it's not helping my confidence for a long cross country.

  4. #4
    rocket's Avatar
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    Default Re: Well I tried to fly today

    Just a quick bit of info:

    one fouled plug is about s 250 rpm drop and a 1k drop usually requires mag work.


    rocket

  5. #5
    rocket's Avatar
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    Default Re: Well I tried to fly today

    So, a little basic plug trouble shooting


    -250 rpm drop is usually one plug.
    Run engine about one minute on bad mag then hop out and feel valve covers, usually it is quite obvious which cylinder is cold. One handy trick is a water spray bottle on each exhaust at the cylinder head being quick about it; spit works in a pinch. Of course one of those digital point the shoot thermometers work well.
    P-leads, I was snookered twice by miss wired pleads before I realized the economy of checking that the mag switch agreed with the mags. When i build leads I would use a length of red and green heat shrink tubing. I also used colored tye wraps or colored sharpi to mark the leads accordingly: red for left and green for right.


    Another time saver is to know which mag fires which plugs. The small lyc split up the plugs with two going to the top on one side and the other two going to the bottom on the opposite. I've seen a couple Cubs wired all on top for one and bottom for the other. Just takes a moment to trace them then you know.


    Now it's almost always the bottom plug that fouls, say your left mag drops, you already know the left fires the bottom right plugs, so you do your bad mag runup, hop over and prop open the right cowl and feel the valve covers and move forward accordingly.


    Tool bag- behind your seat is a tool bag with all you need to change a plug as well as a new or serviceable plug ready to go, of course it will have other tools and bits.
    Armed with all this info, a little pre planning, and a touch of luck and a fouled plug is a two minute affair and you are on your way.


    Oily plugs... It's time to have that conversation with your trusted engine mechanic.


    0-290 just save yourself the trouble and pull bottom plugs and clean every 50 hours as well as study leaning/power settings for lead scavenging. I've seen these lead up and cause issues by thrifty pilots lopping around at low power settings.


    Going mad typing this on my old iPhone 4 so I'll stop here.


    Rocket

  6. #6
    mmoyle's Avatar
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    Default Re: Well I tried to fly today

    My crystal ball prediction...you will find yellowish bits of plastic in one mag...


    Sent from my iPad using Tapatalk Pro

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    Default Re: Well I tried to fly today

    Quote Originally Posted by mmoyle View Post
    My crystal ball prediction...you will find yellowish bits of plastic in one mag...


    Sent from my iPad using Tapatalk Pro

    Bendix mag with distributor teeth coming off?

    Pull the vents, turn the engine over by hand and look for missing teeth?
    Last edited by Vagabondblues; 04-25-2020 at 01:20 PM.

  8. #8
    Flyjeep's Avatar
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    Default Re: Well I tried to fly today

    Im leaning toward a bad mag now. Mechanic at the field will get to it when he finishes his other project. I may still pull the plugs and knock out the busy work. Im going to start buy getting a socket and a couple spare plugs for my tool bag..thanks for all the help.

  9. #9

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    Default Re: Well I tried to fly today

    My guess would be a Slick mag without the latest SB done. I have 60+ hours on one that needs to go back to Slick to get the parts swapped. I keep ignoring it because it hasn’t given me any trouble yet. I have half a notion to swap it for an electronic ignition. (I swapped the other side when it had about 10 hours on it. It needs to go back too).

    Having said that, I did see a Bendix last year that gave similar symptoms. It had about 1300 hours on it with no inspections done since overhaul. A bearing had worn out causing the rotor to miss the contacts.

    The impulse coupler could have failed too.
    Last edited by Jeff J; 04-25-2020 at 05:52 PM.
    "Good judgement comes from experience, and experience comes from bad judgement." - Fred Brooks

  10. #10
    Flyjeep's Avatar
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    Default Re: Well I tried to fly today

    Mine says bendix remanufactured on it. Log book says overhauled or exchanged in 94, 412 hours
    Last edited by Flyjeep; 04-25-2020 at 06:28 PM.

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