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912A exhaust spring problems

in 912 / 914 Technical Questions 14 years ago
I am a happy owner of a Diamond HK36R motorglider with a brand one year old 80 HP 912A engine. With only 150 hours on it, I have replaced the right rear exhaust pipe spring five times, the back side one, and the front spring on the same pipe once. All other springs are lasting fine. The failure is at the beginning of the bend for the attaching loop. Recently at annual, we tried putting RTV on the coils in case it was a vibration problem, but the spring seemed to snap only a little sooner.

  • Re: 912A exhaust spring problems

    by » 14 years ago

    I had spring problems on my new engine until I wired the springs. Use binding wire around the two springs to pull the springs towards the pipe. Just enough pressure to put a strain on the springs to stop the pulsing. I have not broken one since. TRD
      
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  • Re: 912A exhaust spring problems

    by » 14 years ago

    Spring problems seem to be related to individual installations involving harmonics and vibrations peculiar to each installation. I've known people who had constant problems with springs and people who have never had a problem. I solved mine by switching to the spring loaded bolt and collar type connection about five years ago and never had another problem. These are available from any supplier like Lockwood, CPS, Leaf, etc..

    Bill.
      
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  • Re: 912A exhaust spring problems

    by » 14 years ago

    Is the spring bolt system available fo the 912?
      
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  • Re: 912A exhaust spring problems

    by » 14 years ago

    Tim,

    The new clamp system is available for the 912, I have them on mine. Be sure you specify the 912 if you buy them because the clamps for the two cycle engines are for a larger diameter exhaust pipe. They are pricey. CPS sells them for about $45 per joint. You'll never have to replace them though; mine are six years old. You might check LEAF, Lockwood, and Bear Perkins. They might have them cheaper.

    Bill.
      
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  • Re: 912A exhaust spring problems

    by » 14 years ago

    Spring tension can play a big part. i.e. If it is too tight. Many do not add enough silicone. I usually make my bead 1/2" wide and a 1/4" tall to give it some body and strength not to mention working it in between the coils. Another method is to actually fill the spring with silicone. Either way spring tension may be the culprit.

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

      
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