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Thread: CarbMate P-sync tool description

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  1. #1
    Senior Member rv9ralph's Avatar
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    Default Re: CarbMate P-sync tool description

    I used a CarbMate to sync my carbs 3-5 years ago, I will try to remember the process. As you stated, first do the mechanical sync. Then connect the CarbMate using the crossover tube as the connection point with one CarbMate to the crossover and the other to the connection that would normally be connected to the crossover.

    The led lights on the CarbMate show that the vacuum is more or less to one side or the other. The "Ref" is the carb that you decide not to adjust. The other carb is adjusted by turning the adjustment at the end of the cable housing on the carb. By turning the adjustment at the end of the cable you will slightly change the vacuum until the carbs are in such. Start at around 2500 rpm with the sensitivity set to where the faceplate recommends. Then check at higher rpms until you get it the best you can.

    I did the sync alone and did not feel comfortable doing the adjustments with the engine running and shut down between adjustments.

    That is about it, good luck.

    Ralph

  2. #2
    Senior Member Birdseyeview's Avatar
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    Default Re: CarbMate P-sync tool description

    Quote 1: "The "Ref" is the carb that you decide not to adjust.

    Quote 2: The other carb is adjusted by turning the adjustment at the end of the cable housing on the carb. By turning the adjustment at the end of the cable you will slightly change the vacuum until the carbs are in sync. "

    Ralph - Thanks - Your 1st quote above is very helpful. I couldn't find a definition of what the "REF" side was until reading your definition - it now makes perfect sense for that piece of my puzzle.

    Relative to your 2nd quote - do you have a suggestion which way I should adjust "CARB2"? Should I increase or decrease the throttle setting at that bowden cable? Or should I just experiment with both directions until I stumble into the right direction? I like knowing how deep the water is before I dive in. Example: If it should require me to increase the throttle setting of "CARB2" I can do that but I'm nervous that the P-sync may be far enough out that when I do get it balanced that both throttle levers may not hit their full throttle stops at the same time. Is that a problem at the full throttle setting or is it a logical consequence of a normal P-sync and therefore considered as OK as long as the carbs are sync'd? On the other hand, if I need to decrease the throttle settings on "CARB2" there may not be enough butterfly valve angle left to go closed before it stops rotating internally. I guess in that case I may need to start over with the mech sync or move to adjust the "REF" side carb to compensate? Or could I switch the "REF" and "CARB2" by reconnecting the hoses to the opposite sides of the crossover tube. If I did that I'd probably have to redo the mech sync first and start again at the beginning.

    I may be making a mountain out of a molehill but from my questions above you can see that this all gets complicated fast and I hope to document the definitions and rules for all this when I finally get it all figured out. Any further thoughts, recollections, or discussion would be helpful to clarify all this.
    Larry Olson
    Kitfox Series 6 - 1st Flight Oct 2021
    Tri-gear, smooth cowl
    912 ULS

  3. #3
    Senior Member jiott's Avatar
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    Default Re: CarbMate P-sync tool description

    Assuming the mechanical sync is fairly good, I have always found that you can choose either carb, whichever is the most convenient, to do the adjusting. It is never a certain carb that is out of adjustment, it is just that they are not both the same. So you can adjust either carb to bring it into sync with the other. This is nothing new to most of you, but maybe it might help some newbies.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  4. #4
    Senior Member jrevens's Avatar
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    Default Re: CarbMate P-sync tool description

    Quote Originally Posted by jiott View Post
    Assuming the mechanical sync is fairly good, I have always found that you can choose either carb, whichever is the most convenient, to do the adjusting. It is never a certain carb that is out of adjustment, it is just that they are not both the same. So you can adjust either carb to bring it into sync with the other. This is nothing new to most of you, but maybe it might help some newbies.
    Good point Jim!
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  5. #5
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    Default Re: CarbMate P-sync tool description

    I know this post is about using a carb mate tool, but I'll throw this into the mix incase some one reading these messages is wondering what to buy to sync their carbs. I've been using a single vacuum gauge with a T in the line coming into the vacuum gauge. Each line going away from the T has a valve in it. Those lines then go to the ports on the intake manifolds. With it all hooked up, open one valve and you see the vacuum there. Close that valve and open the other and see if both readings are the same. Adjust the linkage so they are reading the same. Even if the vacuum gauge isn't accurate, you will still be able to compare one side to the other, and that's what you are really trying to do. JImChuk

  6. #6
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    Default Re: CarbMate P-sync tool description

    I use a twin engine manifold gauge. I found it to be more finite than the carbmate.

  7. #7

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    Default Re: CarbMate P-sync tool description

    Quote Originally Posted by avidflyer View Post
    I know this post is about using a carb mate tool, but I'll throw this into the mix incase some one reading these messages is wondering what to buy to sync their carbs. I've been using a single vacuum gauge with a T in the line coming into the vacuum gauge. Each line going away from the T has a valve in it. Those lines then go to the ports on the intake manifolds. With it all hooked up, open one valve and you see the vacuum there. Close that valve and open the other and see if both readings are the same. Adjust the linkage so they are reading the same. Even if the vacuum gauge isn't accurate, you will still be able to compare one side to the other, and that's what you are really trying to do. JImChuk
    I used this procedure just last week, rarely are two gauges exactly the same. Using the valves to limit gauge flutter is helpful as well.

  8. #8
    Senior Member Birdseyeview's Avatar
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    Default Re: CarbMate P-sync tool description

    Quote Originally Posted by ScottS97385 View Post
    I used this procedure just last week, rarely are two gauges exactly the same. Using the valves to limit gauge flutter is helpful as well.
    Scott, This is a great idea and fairly easy to create such a tool. I wish I had heard about it before I bought the Carbmate. Thanks for the input.
    Larry Olson
    Kitfox Series 6 - 1st Flight Oct 2021
    Tri-gear, smooth cowl
    912 ULS

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