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912S starting problem

in General Tech Discussion 13 years ago

  • Re: 912S starting problem

    by » 13 years ago

    I found this and copied it:

    Low RPM starting/problem avoidance:

    •Rotax ignition system output power is dependent on engine RPM, low RPM is less power.
    •Car system ignition runs off battery full power (12 volts) all the time, however, if battery goes dead, engine fails.
    •ROTAX ignition separate from battery system and therefore more reliable.
    •Healthy engine requires about 240 RPM to start
    •Typical cranking speed is about 360 RPM for healthy engine in warm weather with fully charged battery.

    Starting problem avoidance
    •Starting problems are typically: •Fouled carburetors from storing aircraft with un-stabilized auto gas because idle jets become fouled (requires carburetor service).
    •Insufficient cranking speed from undercharged battery, loose grounds, or undersized starting cables.
    •Old spark plugs fouled from lead deposits
    •Spring pack in the Torsional damper becomes soft (gearbox requires service)
    •Sprague clutch on starter is worn out (requires service)

    •Starting problem is not typically electric ignition if both ignition systems were functioning properly during your last flight. it is unlikely that your ignition system is the cause.
    •At low starting RPM, can not see spark if cap is pulled to check for spark (as with automobile engines). Spark adequate to start engine but too weak to be seen except maybe in the dark.
    •If you disconnect plugs and try starting this will burn out the stator. Have plugs grounded/plugged in when cranking over engine.
    •When engine is running at idle RPM, plenty of energy to see spark.
      
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  • Re: 912S starting problem

    by » 13 years ago

    Hi Richard,

    What may be crossed is that it takes at least 240 rpm to generate enough energy to fire the plugs, but a healthy engine may turn over as much as 350 rpm when it cranks on a good battery.

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

      
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  • Re: 912S starting problem

    by » 13 years ago

    Thank you. Now I don't feel so bad about my input on the RPM. As I mentioned before, I keep a battery minder connected at all times when the plane is in the hangar. Last October I had a very bad accident at home and broke both ankles. I was laid up for five months before I was able to get in the plane. Even after setting for five months idle the enging started instantly. With out the batteryMinder on it I suspect it might not have done so well.
      
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  • Re: 912S starting problem

    by » 12 years ago

    Hi everybody

    I have a Rotax 912S in a Sonex. He is 400 hours now. It allways had an hard start.
    I have tried everything: new plugs, carb sinc, shock tunning, battery charged and so on.
    After start it runs well with no probleme at all.
    When I simulate a primer by blowing through the pipe that is in the carburator it starts immediately with no probleme.
    One of my partners wants to alter the float in the carburator so the level of fuel in the carb chamber will be higher.
    Is this advisable?
    Is it better to install a simple primer system?
    Is there any other solution?

    Thanks in advance for your help

    Rui Melo
      
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  • Re: 912S starting problem

    by » 12 years ago

    Hi Rui,

    We need a little more info.
    Electric fuel pump?



    Other possibilities to consider;

    How old is the engine (not hours, but age)
    Enricher (choke) opening all the way?
    Mixture screw turned out 1.5 turns?
    Idle set to a proper rpm i.e. 1800+/- rpm?
    No throttle during start? (up to 10% would be acceptable with a low idle rpm)
    Plug gap?
    Newer starter (gold colored) or old starter (black)?
    Possibly a larger wire size between the stater and battery? What is the distance and wire size?
    Battery size?

    I would advise not playing with the float level. Leave it at the stock position. You will open a different can of worms raising the float level. Most likely flooding and venting fuel.

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

      
    Report
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