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912 SMD Soft start ignitions

in 912 / 914 Technical Questions 10 years ago

  • Re: 912 SMD Soft start ignitions

    by » 10 years ago

    Hi William,

    When using the soft start modules the engine now starts after top dead center verses before top dead center. The starter circuit stays in that mode for approx. 6 seconds. It runs rough during this time period. At that point the the timing changes. Is this the vibration you are referring to?

    If it is that is normal for all soft start systems.

    _______________________________________________________________________________________________________
    You already have one of the heaviest props and that could be part of the problem. How long is this prop? Hopefully no more than 68" and no nickle edges. You really don't want a real heavy prop. If anything you would want to go lighter.
    This may or may not be a prop issue, but if it isn't the normal soft start roughness then you can try these.
    Make sure the pitch in each blade is identical, make sure the blades are tracking equally, get a dynamic balance, make sure your rubber engine mounts aren't more than 5 years old (replace them if they are), Make sure the engine mounts bolts are torqued up to proper spec. Make sure the carbs are synced.

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

      
    Report

  • Re: 912 SMD Soft start ignitions

    by » 10 years ago

    Hi Roger,

    Thank you for your input.

    It is not that the engine is running rough. It is the prop kicking back and forth against the gear box dogs in this non-slipper clutch engine during start up. It is actually hard to increase the RPM's while this is going on. With the new soft start ignitions it seems, as you suggested, to have aggravated the problem. I have found a starting procedure that has virtually eliminated the problem.

    1. Crank the engine for a second or two with the ignitions off, Throttle Closed and full choke.
    2. Set throttle about 1/8" from Closed, both ignitions on, full choke. The engine starts and easily spins up to about 2200 RPM and stops the prop from kicking back and forth against the gear box dogs.

    This starting procedure seems to be the best for this 80HP engine.

    Again thanks for your input,

    Bill Campbell
    Fresno, CA.
      
    Report

  • Re: 912 SMD Soft start ignitions

    by » 10 years ago

    So the engine starts right up,but after the start the prop kicks back and forth for a few moments?


    This may be caused by a gearbox issue and maybe it should come off and be inspected, possibly an ignition issue?

    This may be aggravated by a start procedure like flooding, gearbox needing maint, too heavy a prop, carb sync adding to an existing issue? I'm not sure, but would check them all.

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

      
    Report

  • Re: 912 SMD Soft start ignitions

    by » 7 years ago

    Hi I'm going to replace 966726 SDM for a 965444 soft start module
    Is posible to conect the new module in the soft start configuration and de 966726 in the normal conexión?
      
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  • Re: 912 SMD Soft start ignitions

    by » 7 years ago

    Hi Jaime,

    If I understand you correctly you want to put one soft start module and one standard ignition module on?
    If that's what you mean then I would make them both the same. If you do buy both soft start modules and want to only hook one up I would hook both up.

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

      
    Report
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