Hi folks,

assume you pulled the plugs and found them rather light coloured or black and soaked (you decide). Consequently you changed the jetting or the needle position (according to your interpretation of the plugs‘ face). How long does it take until the changes you made show up on the plugs. Are we talking a couple of minutes of flight or test run or hours?

Same with valves. If you boroscoped them and found them all soaked or covered symentrically in grey ash and then made an appropriate change. Will the result show quickly or does it take significant flight time?

Any experience out there on this one?

  • Re: Reading plugs and valves

    by » 10 months ago

    A half hour flight should do it. However plugs only read the last thing, so if you land and taxi back for 5 min you only see the taxi colour not the climb etc. Engine gurus do a "plug chop" say tie the plane down run at full power for 2 min then turn off mags and close throttle, that way they do not change much.

    These days a good wide-band O2 sensor does a good job and yo do not need the subjective skills. Yo can also read during flight at different power settings.


  • Re: Reading plugs and valves

    by » 10 months ago

    Do you have a particular sensor/product in mind that you can recommend. Having an inflight reading sounds somewhat interesting, too.

  • Re: Reading plugs and valves

    by » 10 months ago

    I have not done this for a few years, however I used a DIY kit from Australia that seems to be available now fully built...


    You would need to weld a big nut 17mm if I remember correctly into your exhaust before the muffler, you can put a Blank in it when not using it.

    The kit was battery powered an you can read the A/F ratio as you operate and take notes on where you are lean and where rich.

    This is probably OVERKILL for an engine like the Rotax, all you really need to do is read the plugs and drop or raise the needle one step and see if it is better.

    Rotax have already developed the engine to a high standard, unless you are making modifications to the engine you will not beat Rotax on tuning !



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