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fat avid 912 engine mount

28 posts in this topic

Posted

Larry the short answer is that we don't know for sure.  Ronny Smith said that he suspected oil starvation sometime in the past.  Maybe that was the vibration that you were chasing in the past, the failing pushrod bearing in the process of failing.  But the case fretting was a known issue on engines 912S manufactured before August of 2006.  With the lower compression of our zippers it may not be an issue.  I suspect that Ronny is correct the Zipper had not been one the engine long enough for case fretting to do its work.  It is easy to check for fretting problems and I suggest you, I and others with the Zipper on older engine keep a weary eye on this.  The first sign to check for is a prop that turns harder after shutdown and then easier again after 10 minutes or so.  If that is the case confirmation is made by loosening the cylinder stud nuts right after shutdown, if the prop turns freely again the the fretting is confirmed.

https://www.rotax-owner.com/en/rotax-forum/3-4-stroke-technical-questions/2271-rotax-912-uls-fretted-crankcase

And to answer your earlier question about Dallas that I did not get to, the new engine is doing well, nothing that money can't be a help in massive quantities. About $20000 for a nice round figure.

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Posted

 

Looking good Leni!

Chris, Jack has a great little digital angle finder called an angle cube that allows you to place it on a surface and zero it and then place it on another surface the get the angle; It really is a great tool and he found it on the internet for not too much.  A great addition to any shop if someone is looking for a Christmas present!  Info on the clearances is appreciated since Leni and I were thinking about what it needs to clear the filters.  I should have sent my filters with him. To match CG of my Subie I calculated the 912 prop flange would be at 27", so 1.5" forward of yours.  I am probably used to flying with my CG that far forward but I have always kept my tool box in the very rear of my cargo area, and all my survival gear, food, tent, sleeping bag, etc. in the furthest rear bay of the cargo area so there is at least 40 lbs back there all the time.  It kind of comes down to what kind of hauling we use our planes for?  Anyway, this gives me a solid range between yours and my calculation to decide on.  What do you typically haul in yours in the cargo area when loaded heavy?

Paul, my SN is 6778594. Hal gave me the SN to check and this is a later model engine so I went with the 114 hp kit.  I have always run premium in my Subie anyway so no change for me.  Hal says he runs his at 6000+ rpm in cruise for long periods of time as well and seems to think it gets better fuel mileage at the higher rpm with no issues.  He said he has about 1000 hrs on his high hp kit now so it convinced me to go with that one.  It is just amazing how light the pistons and cylinders are.

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Posted

Alright, I think you will really like the Zipper setup and it is good to hear Hal steered you right as one would expect.  They are great folks to work with.

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