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The 912 UL in my Kitfox IV has 12 hours on it. I have been very happy with the performance so far but have a recurring problem that needs to be addressed. The number one carburator is shifting its clock position by about 5 degrees (give or take). The clamp is tight and I can move the carb by hand to re clock to vertical but I think the fix is simply to remove the clamp stop and torque it down. I have checked the torque on the manifolds and don't find anything loose anywhere. Ideas ?
The Model IV uses reversed manifold positions so the carbs and manifolds are outboard of the engine a little which of course increases arm and moment for vibrations. The engine is sewing machine smooth.
  • Re: Carb loose?

    by » 6 years ago


    Hi Jay,
    If you remove the clamp spacer and tighten it more then you WILL damage and possibly cut the rubber flange. This is why Rotax put that spacer in place to start with. People were over clamping and damaging the rubber flange. Once the clamp is tightened with the spacer in place it should not move. Even by hand it should be hard to turn, but will given a little muscle. If it wants to turn in one direction what is influencing that turning. The carb shouldn't want to turn on its own.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Carb loose?

    by » 6 years ago


    Also be sure that your carb and manifold are fully seated in the connecting rubber flange. It is relatively easy to think that the carb is fully seated when it is not.

    Thank you said by: jay white

  • Re: Carb loose?

    by » 6 years ago


    Ok, I"ll check that and I won't remove the spacer. The slight cant in the carb affects the floats and immediately the balance. Pretty easy to see the symptom show up. I'll let you know.

  • Re: Carb loose?

    by » 6 years ago


    I've had a couple people come in for maint. and the carb would fall out with a one finger push. Make sure it kind of snaps or clicks in place and is seated fully up to the carb housing. There should be no gap.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


    Thank you said by: jay white

  • Re: Carb loose?

    by » 6 years ago


    Ok, The carbs are definitely seated completely, the torque on the screw is just down to the clamp spacer and they are both moving a small amount. I can tell immediately because the carb that is tilted has an abnormal float position and causes the engine to be out of sync immediately. All the engine mounting bolts are torqued to spec and the rubber is all new. I'm thinking of shaving the spacer down 1mm and retorquing. I know you can damage the boot but the boot isn't holding the carbs in the socket. Should I look for something else. I may just do some before and after photos and video. to help you all see what i'm seeing. I think the shutter speed on the video has to be high to keep from making a weird effect. I"ll check back, but any ideas would be helpful.

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