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912 engine 'Blip' just after take-off

in 912 / 914 Technical Questions 12 years ago
I have been suffering an intermittent engine 'blip' shortly after take-off in my EV97 Eurostar for around 9 months. It seems to happen on full power at the top of climb-out, but not on every flight. I've tried all sorts of things in an attempt to remedy the problem, including: 1) Drained and replaced fuel 2) Replaced in-line fuel filter 3)Replaced plug caps 4) Cleaned all electrical connections 5) Replaced fuel pump 6) Cleaned air filters. The puzzling thing is that I had 5 consecutive take-offs, and each time the 'blip' occurred. Someone suggested that it may be the fuel pump, which I duly replaced. Then followed 17 symptom-free take-offs, and I optimistically thought the problem had been solved at last...but no! During take-off 18, the problem returned. Since then, it's happened about every 4th flight or so, although there doesn't seem to be any issue once I'm at cruise revs, and can happily fly around for hours. Please help? I'm getting rather despondent, and I'm also running out of clean underpants!!

  • Re: 912 engine 'Blip' just after take-off

    by » 12 years ago

    Hi John,

    Can you be more descriptive of a 'blip"? What rpm on take off are you getting and or what is the wide open throttle (WOT) setting in a flat and level attitude? Have you tried shallow verses steep
    take-offs? What are the plugs gapped at? How old an engine and have the carbs been synced and or rebuilt?

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

      
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  • Re: 912 engine 'Blip' just after take-off

    by » 12 years ago

    Thanks for the quick response Roger, but be gentle, my technical knowledge is limited. In response: 1) The engine is 10 years old with around 700 hours in total. 2) There doesn't appear to be any difference between a shallow or steep attitude. 3) The flat-out revs are 5,200. 4) The carbs haven't been balanced or re-built in the 6 years that I've owned the aircraft. 5) The plugs were supplied 'pre-gapped' I think. Funnily enough, the current issue was preceded by a couple of broken wires coming from the ignition packs, and around that time I did replace the plugs. I've got it into my head that the problem's fuel related, and that may be sending me up the 'wrong alley!
      
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  • Re: 912 engine 'Blip' just after take-off

    by » 12 years ago

    Hi John,

    Not technically or even mechanically inclined is not a problem. Every experienced guy on this list had a beginning at some time and we're happy to help any way we can.

    Here are a few things to do that may be exacerbating your problem and things that should be done regardless.This may even get rid of the problem. The combination of these may even be the problem and these should be done to rule out and remove these from the equation.
    First plugs don't come pre-gapped for us. You need to reduce the gap that come out of the box down to .023 to .027. The wider gap for warm weather like the summer months and the narrower gap for cold winter weather. The prop pitch is too course if all you get is 5200 rpm at WOT in flat and level flight. Remove and flatten the pitch approximately 1.75 degrees. The carbs are 10 years old with 700 hrs. Does the logbook show that the carbs have ever been rebuilt in its ten years? If not I'm sure they still have the old needle valve. These really need to be rebuilt and cleaned. Every 100 hrs or at the annual these should be synced. My money says if you do these things your problem may disappear, your plane will absolutely perform better in climb, top speed and fuel economy. If your not mechanically inclined no problem. Where do you live and many of us here can probably tell you where a good Rotax mechanic is close to you if you don't already know one.

    Your problem may be simply fuel delivery, but unless you address the above they can be a factor and may cause you issues down the line. These items above are all pretty simple to take care off and your engine will be happier too.

    If you need any more help your welcome to call.

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

      
    Report

  • Re: 912 engine 'Blip' just after take-off

    by » 12 years ago

    Hi John

    As well as doing what Roger says, there could be a chance you have an electrical problem, probably another wire breaking down on the ignition modules.

    I think this is where you should be getting someone to look.

    Mark
      
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  • Re: 912 engine 'Blip' just after take-off

    by » 12 years ago

    Hi John,

    I would still like to know what you're calling a blip? Is it just a one second sputter, something longer, just a slight loss of power?

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

      
    Report
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