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Thread: Early rotax 912

  1. #1

    Join Date
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    Default Early rotax 912

    Hello All, I'm and A&P with lycoming experience, and a flying RV7. I am new to the rotax world. I'm looking to purchase a 1991 kitfox model 3. It has a very early rotax 912 that has not been overhauled since new that I am are of. The plane has been sitting since about 2015, and has about 460 hours total time on it. I know that opinions will range from "run it as long as the compression and oil analysis look good" to "don't even think about touching it until its been overhauled. For what its worth the engine has perfect compression and a bore scope of the cylinders look good. I know this isn't the whole story though. What specific things would you be concerned with on an engine of this age? Crank? cam? gearbox? case fretting?

    Given the idea of an overhaul, do any of the parts from an engine of this vintage have any core value?
    The engine SN is 379(2?)738
    Thanks in advance

    Caleb

  2. #2
    Senior Member
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    Default Re: Early rotax 912

    I was told by the head mechanic at Leading Edge Airfoils that these engines store quite well if kept in a dry place. Nicasil cylinders don't rust for one thing. JImChuk

  3. #3
    Administrator DesertFox4's Avatar
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    Default Re: Early rotax 912

    I owned a 1991 Model 3 with the early version 912 Rotax. Purchased it from the 2nd owner with 230 hours on it. Flew it for a little over 3 years and put over 1150 hours more on it. When I lost track of it after itís sixth owner and near 2,000 hours, it was still going strong and had been untouched internally. If the engine you are considering has been properly maintained, 460 hours would not concern me barring any prop strike history. Iíve seen these engines sit as long as 8 years before first start and fire up as if they just came off the Rotax assembly line. Carbs may need cleaning or possibly rebuilding after sitting that long. Not a big project. Also all rubber hoses may need replacing per Rotaxís 5 year replacement recommendation. Those would be the cooling system hoses, oil hoses and fuel delivery hoses. Also not a difficult project.

    Leading Edge Air Foils (L.E.A.F.), one of our site sponsors and mentioned by Avidflyer, or California Power Systems (CPS), another Rotax dealer and one of our site sponsors, could supply all the parts for carb rebuilds and or hose replacement if needed. Being an A&P, once you learn the proper care and feeding of that engine, it will likely be the most economical engine youíve ever encountered.
    Best of luck to you. Would like to know if you end up purchasing that or any other Kitfox. Welcome to TeamKitfox.com. Glad you found us.


    P.S. The model 3 with a 912 80 hp Rotax is a formidable S.T.O.L. aircraft and loads of fun.


    DesertFox4
    Admin.
    Building 7 Super Sport
    912 ULS Tri-gear

  4. #4
    jonstark's Avatar
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    Default Re: Early rotax 912

    Fly it like ya stole it! YeeHaw!
    Kitfox IV 1050, C180. Now I have two backcountry planes! WooHoo!

  5. #5

    Join Date
    Jun 2010
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    Corona, CA
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    Default Re: Early rotax 912

    Make sure cases and crank are good. The Old none thru bolt cases are no longer readily available. Replacement comes only with cases, crank and cam. $$$$$$
    RV 7A flying.
    Kitfox 7 flying.
    Lucky seven's

  6. #6

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    Jul 2018
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    albury australia
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    Default Re: Early rotax 912

    I am also an aircraft engineer here in Australia and have just brought a model 5 that was ground looped with a 2000 year make 100hp ULS. It has suffered two prop strikes and has 750ttsn. I have carried out the normal gearbox inspection, crank twist and run out with no issues. Mine is pre through bolt and coming from lyco/cons i was concerned about the case fretting. i have since learnt a lot about this and how to check it in accordance with the manual. I would recommend as stated, New hoses, rebuild carbs and maybe a quick gearbox inspection/clean then go flying! they are a tough little engine and with the right maintenance can well exceed their TBO especially the little 80hp

  7. #7

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    Lawrenceville, GA
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    Default Re: Early rotax 912

    How did you carry out the inspection on the crankshaft? To do that you need to split and reassemble the case.

    If you did so I'm interested in the procedure.

    Thanks!

    Quote Originally Posted by JamesD View Post
    I am also an aircraft engineer here in Australia and have just brought a model 5 that was ground looped with a 2000 year make 100hp ULS. It has suffered two prop strikes and has 750ttsn. I have carried out the normal gearbox inspection, crank twist and run out with no issues. Mine is pre through bolt and coming from lyco/cons i was concerned about the case fretting. i have since learnt a lot about this and how to check it in accordance with the manual. I would recommend as stated, New hoses, rebuild carbs and maybe a quick gearbox inspection/clean then go flying! they are a tough little engine and with the right maintenance can well exceed their TBO especially the little 80hp
    Building a KF IV Classic
    Original Speedster Wings
    HKS 700e - Can you say speed demon?

  8. #8

    Join Date
    Jul 2018
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    albury australia
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    Default Re: Early rotax 912

    Quote Originally Posted by napierm View Post
    How did you carry out the inspection on the crankshaft? To do that you need to split and reassemble the case.

    If you did so I'm interested in the procedure.

    Thanks!
    The case does not require spitting for an inspection post prop strike. The procedures are in the manual and the crank inspection requires special rotax tools that include a protractor for the crank and then you then take each cylinder to TDC and measure the twist between all four. This is carried out due to rotax having pressed together cranks. I can attach the manual pages if you like. Also case fretting is a simple pull tq measurement both cold and hot. Both these inspections donít take long.
    James Doyle
    Aussie aircraft engineer
    Series 5 barn find in repair
    912ULS-Kiev 3 blade-round cowl

  9. #9
    Senior Member
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    Default Re: Early rotax 912

    Please attach the manual pages for the prop strike inspection. Thanks, JImChuk

  10. #10

    Join Date
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    albury australia
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    Default Re: Early rotax 912

    6BDEF171-52E3-4566-A7E3-C60DE0569523.jpgE9417579-F3E3-47BC-A43E-A4A1A9EA4208.jpgAB355412-7126-4D58-AD4B-19ABB8BE86BD.jpg C6A8D82B-82A0-4A30-9897-163D918867E5.jpgQUOTE=avidflyer;86686]Please attach the manual pages for the prop strike inspection. Thanks, JImChuk[/QUOTE]

    Please keep in mind this if for an engine with an overload clutch and all my inspections where carried out with an approved rotax service Center. This in not all the pages required
    James Doyle
    Aussie aircraft engineer
    Series 5 barn find in repair
    912ULS-Kiev 3 blade-round cowl

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