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Rough running at 4200 or more RPM above.

in 912 / 914 Technical Questions 10 years ago

  • Re: Rough running at 4200 or more RPM above.

    by » 10 years ago

    Since EGT is supposed to be at a maximum at the stoichiometric ratio, if the mixture becomes either lean or rich the temperature will drop. That said, you can probably see if one cylinder is different to the other three. If a pair of cylinders are different to the other pair then unless you have a reference set of values then it may not be obvious which pair is at fault.

    Kevin
      
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  • Re: Rough running at 4200 or more RPM above.

    by » 10 years ago

    Its somthing to look for: the engine with the partially blocked mainjet ran perfect at idle, and even into the mid range.
      
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  • Re: Rough running at 4200 or more RPM above.

    by » 10 years ago

    Found the problem small debri in the left main jet
    Also both carbs are .5 difference on the gauges is that good enough??
      
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  • Re: Rough running at 4200 or more RPM above.

    by » 10 years ago

    Hi Andre,

    Glad you found your problem.
    The EGT's and a set of sync gauges can help diagnose issues, but sometimes nothing beats a good visual inspection. There was a guy in one of my classes that had a piece of rubber hose just like Rob showed you.
    If you have gauges why settle for .5 difference, you can dial it in with just a tweak and make them equal.

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

      
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  • Re: Rough running at 4200 or more RPM above.

    by » 10 years ago

    Thank all for your help !
    I will tweak the carbs balance tomorrow to get them even,
    During the test the EGT on the left bank was 60degs higher than the right ,that pointed me to the left side been leaner
    I was trying to send you a picture but I don't know how sorry
    Andre with a smooth engine:)
      
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