having 20+ hours of perfect running (on a 200 hr, new to me Rans S6) was on a local flight after 30-40 minutes flight time probably about 4900-5000 rpm thought I felt a slight roughness or extra vibration but as I am still getting used to the high rpm of the Rotax, I was unsure. A few days later I did an especially good preflight and had typical easy start, smooth warm up and taxi, and take off. Maybe 10 miles at 2500' I felt a similar oddness and headed back towards the airport. At about six miles out it felt like the motor stopped (!) I pushed the throttle forward by instinct, and it went back to running fine. Then a couple miles later, just before turning downwind, it happened again ?!!!. Landed and taxied to hanger running fantastic. Carbs were sent to Lockwood for 500 hr check approx 30 hrs ago in 2019. Any advice or ideas appreciated. There are no Rotax mechanics anywhere near me.

  • Re: power loss in flight

    by » 4 years ago

    Who did the carb Install?   You, or another person?

    Were the Carbs re-synced when re-installed?

    It superfically sounds like you are slowly flooding out.

    Were new floats installed?

    Recheck the Float weights.

    The carbs may have been checked 30 ENGINE Hours ago, but the floats sit in the gas for 730 hours a month.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

  • Re: power loss in flight

    by » 4 years ago

    Previous owner had an AnP install and it ran fine for him and great for me for 25 hrs, then yowza.

    I am just learning how finicky and high maintenance 912 s are.

    Hesitation was quite a shock, like both mags were shut off !!! Then back to full power ???

    When you say check float weights, you mean weigh the floats ?  Where does one get a scale to weigh something that small, and how would weight of float cause such a sudden and complete power loss, followed by running fine ?

    Most advise it’s clog in tiny carb passage. If floats decompose, why not change them more often ? 







  • Re: power loss in flight

    by » 4 years ago

    YES you must weigh the floats!!  Just a couple of grams will make a BIG difference (between floating and sinking).  

    You need a scale with precision down to tenths of grams.  These are easily found at certain kinds of shops...


    "1 Let the floats dry for 1-2 minutes, then weigh the floats. Only weigh dry floats.

     2 Check the weight of all affected floats using a calibrated scale. Measuring tolerance of the scale: max. 0.1 grams.

     3 The results of the measurement must be documented in the maintenance records. The max. allowable weight (of both floats together) is 7 grams." (MML 12-20-00, p. 35)


    Incidentally, Lockwood advises that you weigh floats before sending them carbs for inspection.  By the time a carb gets to them the floats will have been out of the fuel too long for them to get an accurate measurement.

  • Re: power loss in flight

    by » 4 years ago

    Hi Dani,

    The 912 UL or ULS aren't finicky. They run very well and are dependable and the only time there is usually an issue is from  poor installs, aftermarket parts and poor maint. either from lack of or someone does things they shouldn't have. If you have issues then find the cause of the issue and not the result.

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

  • Re: power loss in flight

    by » 4 years ago

    I also have a Rans S6S and had a similar problem.
    Have a good look at the carburetor vents.
    The S6S has air coming in the top through the radiator as well as through the front of the cowling, I think it upsets the airflow around the carbs and causes problems.
    I ended up installing a airbox to cure the problem.

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