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Thread: Prop Balance

  1. #11
    Senior Member Slyfox's Avatar
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    Default Re: Prop Balance

    One more thing, if you choose to be able to crank the motor with the mags off, you should be able to install a starter button seperate from your keyed mags switch, that is if you have a keyed switch for everything. I have a starter button on my rv. makes for bring up oil pressure with the mags off, very usefull.

  2. #12

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    Default Re: Prop Balance

    Well Slyfox came over and listened to it- he found one of my chokes slightly open, cleaned the plugs and tried again- same issue as before. So now he has loaned me a prop to try- and the warp drive tool to check mine. Thanks Slyfox!! I will try to get to it on Monday- will update the results.

  3. #13
    Administrator DesertFox4's Avatar
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    Default Re: Prop Balance

    Well Slyfox came over and listened to it- he found one of my chokes slightly open, cleaned the plugs and tried again- same issue as before. So now he has loaned me a prop to try- and the warp drive tool to check mine. Thanks Slyfox!!

    Steve's a good man.

    Hope you get to the bottom of this problem.



    I agree on the ignition switches and start button. Love that setup.


    DesertFox4
    Admin.
    7 Super Sport
    912 ULS Tri-gear


  4. #14
    Senior Member Slyfox's Avatar
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    Default Re: Prop Balance

    I didn't point out when listening to the engine, but the older 912ul engines had a distict whirl noise. My old one did it and I heard it out of yours. I still say that prop of yours has a problem. it sure had a nasty wobble when watching it from the side. really hope we can get to the bottom of your problem.

  5. #15

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    Default Re: Prop Balance

    Well- checked the pitch on the warp, and it was perfect. So I pulled it off and put on Slyfox's known good prop(powerfin), crossed my fingers and fired it up- and got no where

    Went back to the basics, compression check, pulled valve covers, rechecked plugs, out of ideas. About ready to order a 100 horse and start over

    So next stop Jim Scott Aircore Aviation on Friday hopefully as I am at a complete loss.

  6. #16
    Administrator DesertFox4's Avatar
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    Default Re: Prop Balance

    Scott- do you know the history of this engine such as did the first owner run 100LL or auto gas? I heard tell of a 80 hp Rotax up in Utah that had lots of trouble after running 100 LL without using the lead scavenger additive and experienced a lot of rough running issues. He finally did a tear down and found lots of lead deposits causing the problems. Just food for thought. I know your getting frustrated as all the tried and true fix's are not helping.
    Best of luck. Keep us updated.


    DesertFox4
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  7. #17

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    Default Re: Prop Balance

    Quote Originally Posted by DesertFox4 View Post
    Scott- do you know the history of this engine such as did the first owner run 100LL or auto gas? I heard tell of a 80 hp Rotax up in Utah that had lots of trouble after running 100 LL without using the lead scavenger additive and experienced a lot of rough running issues. He finally did a tear down and found lots of lead deposits causing the problems. Just food for thought. I know your getting frustrated as all the tried and true fix's are not helping.
    Best of luck. Keep us updated.
    It did run 100LL exclusively from day one, but it only had 145 hours on it when I got it, and now it has 154. I guess I can't count anything out at this point. Dynamic comp test shows #1 124, #2 136, #3 126, #4 135 and differential shows 78/80 all around. Like I said, I am at a loss, multiple people have looked at it so now its down to the Rotax expert I still think I might have the same problem as Larry-

  8. #18
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    Default Re: Prop Balance

    Scott,

    Steve mentioned, your prop had a "nasty wobble" when looked at from the side - did his known good prop also have the same problem?

    You mentioned the problem went away after having the gear box rebuilt. Is this the same , identical problem you had prior to that (reoccurred)? Or is this something that has cropped up since?

    Greg

  9. #19

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    Default Re: Prop Balance

    His was the same- I think it was just the light playing tricks on us as it was getting kind of dark out when we were running it up. This is the same problem I had originally before the gearbox rebuild, however it is much smoother than it was before. When I got it back I still had not been able to listen to some other examples so compared to what it was before the rebuild, it was much smoother(before it shook so bad the carbs puked fuel out of the breather hose), however, now that I have been around a few other Rotax's, it is not as smooth as it should be. I am impatiently waiting for Larry's parts to come in so he can be the guinea pig

  10. #20
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    Default Re: Prop Balance

    You and Larry may have 2 completely different problems. He keeps describing vibration and you seem to generally refer to rough running. Although either could be symptomatic of a prop, gear box, crankshaft issue and/or a fuel, fuel/air mix, detonation problem.

    If you want to rule in or out the vibration aspect, I'd suggest the same thing as I did for Larry - checking the prop hub and crankshaft for true/endplay and runout.

    Very few issues originate with the gear box, but that is what gets damaged 1st, due to other balance, true, vibration source issues. Unless of course you have high time and it's simply wear. Yours has very low time.

    Can you find out from Aircore what was worn, out of spec, replaced when they rebuilt the gear box? Did they give you any explanation on what was wrong with it and their thoughts as to why? Did they actually rebuild it or just inspect it?

    You could be "chasing your tail" and might end up rebuilding it again if the source of the problem originates either in front of or behind it.

    Can you video (with sound) and post to YouTube - it's awfully hard to get a good idea from descriptions.

    Good luck, I know how frustrating these things are.
    Greg

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