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Thread: Carb sync? Never again.

  1. #31
    Senior Member
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    Mar 2009
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    Summerland BC Canada
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    411

    Default Re: Carb sync? Never again.

    OK, here's an update for anyone interested.
    Today I started from scratch.
    Checked all cables for free movement.
    Set throttle at minimum idle and adjusted idle stops for .004 clearance.
    Then closed the idle stop screws about two thirds of a turn.
    Set the mixture screws open one and half turns.
    Left the balance tube connected. Started engine and warmed up to operating temperature .
    Carefully adjusted both idle stop screws to give a smooth running engine at desired RPM. I set mine at about 15 or 1600 with throttle pulled completely back.
    Then I shut down and connected the Carbmate directly to the balance tube nipples.
    Restart but do not idle the engine. Keep it above 2500 or so and run up to 3500 or 4000 . Adjust the cables to put the GREEN in middle at the most sensitive setting through these high RPM s This may take a few restarts and fine adjustments but it is worth it.
    Remove the carbmate and reconnect balance tube.
    My engine seems to now run smoother than it ever has and that is saying something!

    After considerable time attempting to balance with the carbmate attached through ALL
    RPM ranges I have come to the conclusion that it is more effective to get a smooth idling engine by adjusting the idle screws with the balance tube connected. My thinking is if the ide is SMOOTH that is more important than where the green light is!

    Anyway did a few circuits in 30C Temps tonight and it performs super smooth through all RPMs.
    This a long winded explanation that may not be by the book and may not work for everyone but my old 912UL likes it.
    Thanks for comments especially from Mangy that really got me thinking.
    Cheers
    Don

  2. #32
    Senior Member Rodney's Avatar
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    Jan 2009
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    Hugo, Oklahoma
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    226

    Default Re: Carb sync? Never again.

    Ok. I had to try this balance tube thing. Been hearing n reading about it for over a year.

    I have never been able to get my engine to idle smoothly much below 1800 rpm

    I made one from 1 1/2" pipe just for the heck of it.

    Wheels, I don't know if this is old technology or new technology, but IT WORKS.

    I installed it this afternoon and started it up. Let it warm up, but hey when the oil starts out at 90 degrees it doesn't take long. Started backing down the throttle.

    Finally hit the low speed idle stops at 1400 rpm. Super smooth. I can't hardly believe it.

    Am going flying this evening before the sun goes down, but for now am really pleased.

    Rodney

  3. #33
    Senior Member Slyfox's Avatar
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    Dec 2008
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    felts field, spokane
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    Default Re: Carb sync? Never again.

    I'm in the process of redoing my fox. I'm turning it into Badassfox. I installed the Desser 27 1/2 tires. I'm installing the T-3 spring set for the tailwheel. currently the 8inch wide tire from Matco is being built, should be here next week. I put on the balance tube last night and it is real nice. flew it this morning and yes much less vibration. the stick is nice and vibration free. I like it. coming into land there was no vibration. I generally come in real short and pull back to about 500rpm and I didn't feel anything this morning, I thought the engine quit, but it was running. now those tires. makes the look on the plane as well as ground ops is way cool. I sit up much higher. ha, watch out I'll eat you up. haha.http://www.teamkitfox.com/Forums/album.php?albumid=493
    steve
    slyfox
    model IV 1200-flying
    912uls
    IVO medium in-flight
    RV7A-flying
    IO-360
    constant speed prop

  4. #34
    Senior Member
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    May 2011
    Location
    MN
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    469

    Default Re: Carb sync? Never again.

    Rodney,
    Did you drill out and retap the manifolds, or did you put and adapter to the factory port?
    Pictures would be helpful!

  5. #35
    Senior Member Rodney's Avatar
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    Hugo, Oklahoma
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    226

    Default Re: Carb sync? Never again.

    I used the existing ports. I wasn't sure that would work,but I thought I would try it and let the engine tell me if it liked it. So far it seems to work fine. Am headed to the airport shortly to fly. Will pull the cowl n take some pictures

    Rodney

  6. #36
    Senior Member Slyfox's Avatar
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    Dec 2008
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    felts field, spokane
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    Default Re: Carb sync? Never again.

    If interested, you can go here and look at my setup for the balance tube.
    http://www.teamkitfox.com/Forums/album.php?albumid=494
    steve
    slyfox
    model IV 1200-flying
    912uls
    IVO medium in-flight
    RV7A-flying
    IO-360
    constant speed prop

  7. #37
    Senior Member
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    Oct 2016
    Location
    Western Australian
    Posts
    218

    Default Re: Carb sync? Never again.

    http://www.rotax-owner.com/en/rotax-...hro-carb#16469

    Just chucking this out there and don't know if it's useful or not. I'll be getting the 912iS, so none of those nasty carb things for me

  8. #38
    Senior Member
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    Jul 2011
    Location
    milwaukee wi
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    490

    Default Re: Carb sync? Never again.

    What if you used a piece of 1 inch water or fuel rubber hose, with no metal tube?

  9. #39
    Senior Member Wheels's Avatar
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    Oct 2010
    Location
    Spokane Wa
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    420

    Default Re: Carb sync? Never again.

    I don't actually know why the tube is metal except for the nipple that is on some of the metal tubes used for MAP. My old tube is metal and has no Manifold Pressure attach point. So I think If I had a rubber tube, it wouldn't matter. But I have a question.
    If a person used a large diameter crossover tube and simply adapted the size for the existing manifold fittings without making them larger, As Rodney did, why wouldn't that do the same as enlarging the fittings? I understand that the air in the crossover tube is largely static, so the benefit is not in "bernoulli, or venturi, principle but rather from the larger mass of air in the tube giving a "buffer" area to the molecules in transit from acceleration to static. Have I been watching to many re-runs of Star Trek, or am I actually ... close?

    P.S. My mom used to say "better to be judged a fool than to open your mouth and remove all doubt." ... I never listened to her. Maybe I should have.
    Last edited by Wheels; 08-18-2017 at 07:27 PM. Reason: Just realized Rodney did that

  10. #40
    Super Moderator Av8r3400's Avatar
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    Merrill, WI
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    3,044

    Default Re: Carb sync? Never again.

    Quote Originally Posted by mr bill View Post
    What if you used a piece of 1 inch water or fuel rubber hose, with no metal tube?
    The Aluminum tube is lighter, that's why I used it.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

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