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I have an issue with the right engine on my AirCam. I would greatly appreciate any advice you could.

The issue has presented itself three times so far:

  1. Once, during a level flight at about 7,500 ft, and
  2. Again, after a touch-and-go at our home airport in Guaymaral (SKGY)
  3. Yesterday, in a testing flight over the airport.

All of these times, the engine was running at around 3,800 to 4,200 RPM, and suddenly, the RPM dropped to between 2,300 and 2,900. When I attempted to increase power, the throttle had almost no effect.  After a minute or two, the engine recovers its full power.

For context, the carburetors were serviced entirely, and the mechanical fuel pumps on both engines changed after the first occurrence.  The next occurrence was just two days after the service, during a touch-and-go at Guaymaral, right before entering the downwind leg. I landed immediately, and after a visual inspection for leaks or abnormalities, I restarted the engine, and all parameters appeared normal again.

After the second occurrence of the issue, I decided to inspect the tanks, piping, and electrical connections. However, nothing unusual was found during these inspections. The local mechanics are still uncertain about the root cause, though they are suggesting the ignition module might be the problem. I have my doubts about that diagnosis and am exploring other potential causes.

Do you have any ideas about what might be causing this sudden RPM drop and throttle response issue? I would greatly appreciate any advice or insights you can provide.

  • Re: RPM Drop in 912ULS

    by » one week ago


    Since you've had recent maint. on the carbs have you dropped the carb bowls and looked for debris? This should be your first check. This can cause your symptoms.  have you put a set of carb sync gauges on that engine to look for any abnormalities? Take the fuel lines off on that engine at the carbs and flush them out for a few seconds to make sure you have no debris in your lines.


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


  • Re: RPM Drop in 912ULS

    by » one week ago


    Thank you Roger, we did drop the carb bowls and cleaned them thoroughly. We also put the carb sync gauges and they run very smoothly.  We will take the fuel lines off on that engine and flush them as you suggest.  I will report back!

    Thanks again Roger!

    Francisco

     


  • Re: RPM Drop in 912ULS

    by » one week ago


    Hi Roger, I just checked with the mechanic, and he confirmed he did flush the lines when he re-checked the carbs for the second time... I am running out of ideas!  Any thoughts?


  • Re: RPM Drop in 912ULS

    by » one week ago


    Francisco...try replacement of the spark plugs and also remove and replace the spark plug ends after you check the resistance.   Cut the plug wire back about 4 to 5 mm then reattach the connectors with some lithium grease on the plug wire end.  (they thread together)  You may have a loose connector.  Check the connections at the coil also.  

    Cheers


  • Re: RPM Drop in 912ULS

    by » one week ago


    Check that there is nothing inhibiting the free movement of the Slides in the Bing Carbs


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