fbpx

 

Recently overhauled 914 F2/S1 engine installed in S-10VT starts smoothly and idles without any roughness but as throttle is advanced about half way forward rpm smoothly increases up to 3000 rpm and goes no further.  Engine begins running rough when throttle is advanced beyond this point and RPM will not exceed 3000 rpm.  

Experienced IA’s familiar with this engine just installed 2 new rubber gaskets on both carbs.  Both Bing Carbs removed and taken down / inspected for leaks & proper assembly twice now.  All induction / air box / inter cooler connections double checked and confirmed tight.  TCU self tests when initially powered.  TCU throttle position verified using TLR software by rotax service station.  Fresh 100LL fuel, new fuel filters installed.  Fuel lines deliver equal and positive fuel pressure to both carbs.

Motor glider completed annual inspection last month.  Engine test run / mags checked good at 4150 rpm. Aborted takeoff last week when only 5100 rpm achieved with full throttle (30C / 1395’ elev).   Began checking for induction leaks / installed new rubber carb gaskets after aborted flight.  Performance has now worsened / degraded to 3000 rpm limit now after throughly going over carbs and induction system integrity.

Any ideas on how to further troubleshoot? Sensor problem somewhere?

 

  • Re: Stemme 914 F2/S1 low power

    by » 3 months ago


    I do know an individual who had a mysterious problem on a 914.  It ultimately turned out to be someone had over torqued the bowls on the carbs which bent something that caused an overly rich situation.  The problem was isolated/diagnosed by having a shop install a spare test carburetor.  

    The owner told me the the engine ran rough in the mid rpm range and supposedly the bowl was interfering with the high speed jet. --So something you may wish to  check.  I'd take a careful look at the bottom of the bowl.

     


  • Re: Stemme 914 F2/S1 low power

    by » 3 months ago


    You did not mention your float-bowl bolt torques. Definitely check those.  I believe it's supposed to be 48 in-lbs.  Too much can distort the bowl and cause problems as Chris described, above.  Too little can mean a bad seal.  If you suspect distortion, you might want to try a pair of new bowls (and new bolts).

    I also seem to recall that some float bowl bolts were just a little too long and were thus causing problems with the seal.  I know there's a thread on that somewhere here...


  • Re: Stemme 914 F2/S1 low power

    by » 3 months ago


    Both float bowls were confirmed to be straight with a flat edge and properly torqued at 48”lbs with new rubber seals added.


  • Re: Stemme 914 F2/S1 low power

    by » one month ago


    This 914 ran fine using paper filters sealing carb bowls before overhaul.  Read that new rubber float bowl seals are thinner and that bolt might need to be trimmed so that 48 in-lbs torque creates air tight seal. Going to check...


  • Re: Stemme 914 F2/S1 low power

    by » one month ago


    guessing you have a manifold pressure gauge , having the same issue on my S12  , installing a MP gauge soon as it  arrives, suspect waste gate stuck open

     


You do not have permissions to reply to this topic.