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Thread: Rotax 912 UL Back from Zipper Big Bore

  1. #1
    Senior Member bbs428's Avatar
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    Default Rotax 912 UL Back from Zipper Big Bore

    My engine has returned from Zipper Big Bore!

    Discaimer - I am not affiliated with ZBB. I received no consideration for anything I say good or bad.
    I never have met anyone nor know anyone who works for ZBB other than what's been said here, in this post,
    these forums and video's of Hal Stockman and the ZBB engines flying in various aircraft.

    Also please excuse this wordy post...

    I purchased the engine used, with the 1998 outback kit. Came out of a wrecked kitfox IV. No logs with only the
    seller claiming 270 approx. hrs and no prop strike. I like to believe everyone... but I'm old school - trust but verify.
    That being said the hobbs did read 273 hrs. (the hulk and instrument panel of the old IV was in the corner of the
    hanger.) The engine and the propeller were not all banged up. The old motor mounts were bent but not broken.
    The compression checked out and it turned over easily with the plugs out. The oil looked and smelled good. I am
    comfortable saying I valued the engine at about 3K.
    Still a big gamble and a lot of money if it turns out to be junk!

    I thought it was just a bit foolish to install an engine from a very questionable background on a new aircraft and
    expect perfection, so I started talking to Jay Stewart from Zipper Big Bore and decided to ship ZBB the engine.
    Hal Stockman was great to deal with and talk to. He has a lot of experience with this engine.
    I'm a very good Ford FE engine guy but as I had Zip, Zero, Nadda experience with the 912 and now was not the
    time to cut costs. Bottom line was I wanted to have confidence in the engine, make 100+ hp and run on 87 octane
    fuel. Hal spent a lot of time on the phone with me as the engine, gearbox were torn down and inspected. As well
    as when it was on the test bench running. Great customer service!

    What we found out that the engine was in fact low time, older 912 that was mfg. in 2001. So far so good...
    The engine was torn down and checked for any damage, none found. Ok, that's better...
    Crank and heads were checked and looked great. Wow! that's a relief...
    I chose to have Hal machine and thru bolt the case and make it heavy duty. It was not necessary but I thought this
    would be a good long term investment as displacement was increased by 30 hp.
    The Zipper High Torque 1484cc big bore kit was installed as well as a new high profile cam, rocker shafts polished,
    cleaned up the valve seats, new fuel pump, new radiator cap, ignition mounts, hoses, fuel lines, magneto cover and
    a new inline thermostat. Carburetors were set inboard and installed a new larger manifold crossover, installed new
    float bowl gaskets and new air filters.Gearbox was torn down, checked for any damage. None found. Installed new
    slipper clutch, bushings, o rings and seals, magnetic drain plug and re-shimmed.

    Engine bench tested with no discrepancies except the old starter died and was replaced. I made new log books on the
    gearbox and engine documenting in detail all work performed. Time set to Zero.

    I know some of your eyes are rolling into the back of your heads so I'll conclude by saying I did spend more than
    Initially wanted to. However I'm confidant in my engine now. Total cost came in at about 9.4k. So I have approx.
    12.4k in a virtually new, zero time, 110hp engine that weighs in about 140 lbs. Sweet.

    At this price point I'm comfortable with what I spent considering what a new 912uls or 912ils costs.
    Did I spend to much?
    Could I have done more work myself and saved a few $$?
    Was it worth the $$ to have an experienced Rotax mechanic perform the work on this engine?

    You be the judge.

    Yes! I will paint the case, cylinders and rocker covers as well as polish and buff a few items. The engine looks a little sad
    in it's dated 2001, 80hp look. More on that later!
    When I maiden the aircraft and lift off for the 1st time... I can only hope that it's money well spent and with any luck,
    my shorts will remain unstained.

    Attachment 21707
    Attached Images Attached Images
    Somebody said that carrier pilots were the best in the world, and they must be or there wouldn't be any of them left alive. — Ernie Pyle

    Brett Butler
    Flying: 1998 Model 5 Outback, 912ul Zipper 110hp, G3x avionics, ss7 upgrades

  2. #2
    Super Moderator Av8r3400's Avatar
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    Very nice. I am also happy Zipper owner and operator and will vouch for Hal as being an honest and very good guy to work with.

    My Zipper is the 105 hp, low compression, stock case and cam version.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  3. #3
    Senior Member
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    I put on a set of the 105HP Zipper cylinder/pistons on an old 80HP motor. Definitely like the added power.

    I see what looks like the blue silicone water coolant lines with clamps that don't have screws (constant tension). I never thought of using them. HAs anyone else used them without issues?

    Guess I'll start another thread since I am in the process of replacing the hoses.

  4. #4
    Senior Member jrevens's Avatar
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    That's what Rotax uses, Keith.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  5. #5
    Senior Member
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    John, my old motor has the standard black rubber type hoses. How long have they been using the silicone? Surprised they are still recommending the 5-year replacement if they are using better hose material. Oh, it's all about the money!!

  6. #6
    Senior Member jrevens's Avatar
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    I was referring to the clamps. As far as I know they don’t use silicone hoses.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  7. #7
    Senior Member efwd's Avatar
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    All my hose material was provided by Kitfox. I don't recall a single hose supplied by Rotax.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  8. #8
    Senior Member kmach's Avatar
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    New Rotax engines come with black rubber 17mm coolant lines from water pump to heads and from heads to expansion tank. They use a black spring constant tension clamp on these lines.

    When I did the five year rubber replacement I switched to blue silicone hose for the 1" coolant lines, with automotive spring clamps, I used silicone to and from the heater as well and for the thermobob bypass line.

    I decided to buy bulk 17mm black Rotax hose from Rotech , for to and from the heads.
    Kevin,

    Kitfox Outback
    912 ULS
    Airmaster AP332CTFH-WWR70W
    Summit Aircraft Wheel Skis
    C-FOXW

  9. #9
    Super Moderator Av8r3400's Avatar
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    I used 5/8” heater hose from NAPA on mine. Works awesome, no leaks and at a fraction of the cost of 17mm.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  10. #10
    Senior Member AirFox's Avatar
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    Default Re: Rotax 912 UL Back from Zipper Big Bore

    I used 5/8" silicone hose from https://www.siliconehose.com/. Works great.
    Scott Noble
    Kitfox SS7

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