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Thread: 912 Big Bore

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  1. #1
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    Default 912 Big Bore

    I'm in the garage putting bigger jugs on my 912. Thanks to Lowell Fitt (Highwing) and Hal Stockman. The game will be on, but I'm not sure how close attention I'll pay (Packers are not in the game).
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    Last edited by mr bill; 02-02-2014 at 03:10 PM. Reason: add pictures

  2. #2
    Senior Member SkyPirate's Avatar
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    Default Re: I'm watching the Super...

    Looking good Mr Bill, cant wait to see your reports after completion
    Chase
    Model 5 OutBack
    912 UL

  3. #3
    Senior Member Dorsal's Avatar
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    Default Re: I'm watching the Super...

    Good stuff Mr. Bill, definitely more interesting than the game (Pats not in it, no reason to watch).
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  4. #4
    Super Moderator Av8r3400's Avatar
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    Default Re: I'm watching the Super...

    Gonna need a full PIREP on that bad boy once it's running!!
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  5. #5
    SWeidemann's Avatar
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    Default Re: I'm watching the Super...

    Mr. Bill,

    I'm curious about what you are doing to your 912? Is this engine a rebuilt one?

    Skot

    Quote Originally Posted by mr bill View Post
    I'm in the garage putting bigger jugs on my 912. Thanks to Lowell Fitt (Highwing) and Hal Stockman. The game will be on, but I'm not sure how close attention I'll pay (Packers are not in the game).
    Kitfox Vixen 912 ULS
    N24V at C29

  6. #6
    Super Moderator Av8r3400's Avatar
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    Default Re: 912 Big Bore

    Fellow Kitfoxers, I moved the above posts to their own thread because this is going to have some good information that we will want to find again later.

    Mr. Bill, Can you please give us some more details of what you are doing so that we can all learn more about this option for more power?
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  7. #7
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    Default Re: 912 Big Bore

    I bought a late 2006 Rotax 912ULS engine with 36 hours TT. It had a prop strike with the previous owner, with one blade broken on a wooden prop, so I thought there was not much risk. The engine was installed and firewall forward was done. Recently I heard about big bore kits and after some brief research, bought one from Hal Stockman in Elko Nevada (recommended by Lowell Fitt) that increases the engine displacement to 1884 CC. He estimates horsepower increase to 104 and will be doing dynamometer testing in a few weeks. After pulling the old jugs, I found deposits from 100LL on the pistons, cylinder heads and exhaust valves. I bought the low compression version (9.7 to 1) so I can use auto regular. Then I thought that as long as the jugs are off, (an old story) I'll install the new flywheel, for easier starting and the oil pump conversion to increase the TBO to 2000 hours. Then I took the gearbox to Leading Edge Airfoil for a teardown and inspection and they found the propeller shaft flange was bent from the prop strike, so a complete rebuild was done. They also overhauled both carburetors. The engine is back on the plane and the cylinders , gearbox and oil pump are installed. Two steps forward and one step back. Now I know what the engine is. First start is still several months away.
    Last edited by mr bill; 02-03-2014 at 08:16 AM. Reason: add carb

  8. #8
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    Default Re: 912 Big Bore

    Mr. Bill, you say that the prop shaft was bent from the prop strike. Did you ever put a dial indicator on the prop shaft before it went to LEAF? I guess I'm wondering if it could dial straight on the prop shaft hub, but still be no good. Thanks , Jim Chuk

  9. #9
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    Default Re: 912 Big Bore

    First they used a dial indicator on the propeller shaft in the case and then again in a v block after disassembly. The shaft was not bent, just the propeller flange. They replace clutch parts, which is required after a prop strike. They also went thru the cylinder heads completely. They cleaned up very nicely. Inside of the crankcase was beautiful, as expected with 36 hours TT. In my earlier post I said 1884 CC, should have read 1484 CC.
    Last edited by mr bill; 02-03-2014 at 10:08 AM. Reason: flange info

  10. #10
    BigJohn's Avatar
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    Default Re: 912 Big Bore

    Two of my friends in S. CA have the Big Bore Kit's on, One was the 912ULS 100hp that went to around 114 and made a good bit of difference in his ability. Another was the 912 UL 80 hp that went to 104hp and it made a major difference in his performance, Wayne Flemmington of Rotax Service located in French Valley is installing these as well 951-255-9144, Once mine is ready for topend I will be putting it on.
    BigJohn
    Kitfox 5 Outback
    Rotax 912ULS With 1622cc Big Torque Zipper Conversion

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