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Hi,
Aircraft is an Ikarus C42. Rotax 912-UL

Symptoms are misfiring on no 1 & 4 cylinders. Occurs whether on mag1 or mag2.
All wiring has been resistance checked.
'Black Boxes' have been swapped out with another engine. Continuity carried out on all wiring. All ok.
Changed all triggers, checked all pins in plugs for corrosion, swapped the stator wires from 1 to 2, swapped coils from 1 to 2.
Compression check on all cylinders - 140 to 160 psi.
Rocker covers removed for broken valve springs etc.
Checked all wiring to mag switches.
Replaced spark plugs with new ones.
Removed plug caps and resistance checked coils and caps. All ok.
Still same fault on cylinders 1 & 4, misfire, rough running. Removing plugs 1 & 4, both black.

Any ideas as what more can be checked before paying $$$ for stator or new coil to see if this is the problem.

Thanks in advance

Michael
  • Re: Misfiring on 1 & 4

    by » 11 years ago


    Mike,

    Doesn't sound like a bad coil or stator. That usually affects #1 and #2 or #3 and #4.

    #1 and #4 are on separate systems and you would have to have two bad coils. Not likely.

    Have you checked the plug wires themselves? Sometimes unscrewing them and screwing them back in will help.

    Could even be dirty or unbalanced carbs maybe?

    Bill.

  • Re: Misfiring on 1 & 4

    by » 11 years ago


    It is most likely the carb(s) are too rich or too lean or some other carb cleaning or maintenance issue.
    Check this first before going back to the ignition.

  • Re: Misfiring on 1 & 4

    by » 11 years ago


    Hi Michael,

    I agree with Rob. Check the carbs first and they may need to be stripped and cleaned and if you have just done a hose change or the carbs haven't been cleaned for years then I would just yank them both and give the a good cleaning and start fresh and remove any doubt about ruling in or out on the carb influence.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Misfiring on 1 & 4

    by » 11 years ago


    Thanks guys,

    Will go back tto the carbs as has been suggeste, strip, clean / rebalance and check mixture.

    Plug wires were swapped over from another C42.

    Will reply with any success :D .... (or otherwise)

    Michael

  • Re: Misfiring on 1 & 4

    by » 11 years ago


    Hi Guys,

    This issue has lasted for almost 1 month now, so with that thought in mind, a quick apology to Bob for rejecting the leads idea, since they had been swapped..... Well they sort of had....

    Whilst going over the carbs, it was remembered due to time and difficulty swapping all leads a few weeks ago (the other aircraft was needed). this possible cause wasn't completely ruled out, as not every lead was changed!

    Sure enough, removal of all the plug leads today resulted in finding 2 leads which had varing degrees off stiffness along the length of the individual lead. Something "wrong" with these leads compaired to the others....
    So complete set of leads ordered with high hopes the issue will be resolved.

    Will update when they arrive and are fitted.

    Cheers
    Michael

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