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Suggestion for, & question on carb sync tool & kit

in 912 / 914 Technical Questions 11 years ago

  • Re: Suggestion for, & question on carb sync tool & kit

    by » 11 years ago

    Hi Roger,

    Your comments are always interesting and appreciative.

    Just a little curious to know more about your comment:

    "I can look at the gauges and tell if they are sync-able like they are set up or if a cable needs adjustment at its attachment point. (wide needle spread on the gauge) I can tell if an idle jet is clogged or a main jet, or which carb I want to adjust over the other, ect...

    Can you please share how to compare if the idle jet or the Main Jet is clogged by merely looking at those vacuum gauges? Because all they will tell you is the carbs do not pull the same vacuum.. Or any I wrong?

    Merry Xmas and Advance Happy New Year.,

    Andre'
      
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  • Re: Suggestion for, & question on carb sync tool & kit

    by » 11 years ago

    Hi Andre,

    It has to do with gauge needle separation. This is in general terms and as a demo and takes into account the carbs were setup correctly on the mechanical side before the start. If the needles on the gauges at idle are 1-2 " of vacuum off that can be adjusted for. If they are 8"-12" different then they can't be adjusted for and the idle circuit has a clog in the carb with the highest vacuum. This again takes into account they are setup manual correct before the start. You might as well stop right there and clean the affected carb. It will take less time to buckle down and just clean the carb than trying to sync them and after all the fooling around have to clean it any way. If I start the engine and run it up to let's say 3500 for the high rpm sync and they are 1" vacuum out that can be adjusted for with the Bowden cable adjuster. If they are 4" or more out then the adjuster won't have enough travel. Might as well shut down and shorten the cable with the lowest vacuum at the throttle attachment screw on the throttle arm. This will usually help facilitate the idle rpm sync too. If I start the engine and one carb is 1" lower in vacuum than the other carb then I know to adjust the one with the lower vacuum and reduce it's vacuum to the other carb's higher vacuum. In other words if one carb is at 5" of vacuum and the other at 6" of vacuum the one with 5" is getting more air flow than the one with 6". I will adjust and pull back the bowden cable adjuster on the one with 5" to match the one with 6". Many times if you go the other way (6" to 5") if will mess up the idle rpm sync and not allow you to retard both carbs and to get a low enough idle rpm and it may keep you idling up at 2000+ rpm. If you advanced the throttle to 3500 rpm and the gauges are 1" off it can be adjusted for, if they are 3" you need to shorten the cable on the throttle arm. If the gauge needle split is 8" or more time to clean. These are just general numbers to demonstrate what I was talking about and can vary so some experience does help.


    These are only general statements just to show you what gauges can do over an electronic device and some times other corrective actions may need to be done. For me gauges are far and above easier to use and much faster. Just make sure both gauges read equally.


    The other big tip is to do your carb sync at every 100 hr. or annual. That will make each carb sync easy and short because they shouldn't be far off and your engine will run better and stay healthier because the left side won't be trying to oppose the right side with differing rpms. The cross over tube can only do so much. It isn't a cure all for not doing a carb sync.

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

      
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  • Re: Suggestion for, & question on carb sync tool & kit

    by » 3 years ago

    I used carbmate and I really liked it. for those that consider buying the carb mate - I bought a barebone version. It comes with 2 lengths of 1/4 ID vacuum hose attached. If you want a longer hose (I may do it in the future to have carbmate reach the cockpit) - autoparts store will sell you 1/4 in fuel hose at under 50c/foot, cheaper than any aero retailer I know.

    Now for the fun part - Rotax adapter: Instead of forking 60 bucks for one made by carbmate people I used uxcell 12mm to 4mm Hose ID Brass Reducer Barb Hose Fitting Straight Connector Coupler Tubing Adapter 3pcs: Amazon.com: Industrial & Scientific - 10bucks for 3 adapters! you get to keep a spare.

    Then I used 2 short pieces of 7/16 ID hose (auto parts store, cheap), and attach to both carb crossover tube fittings, as that is easier to me than to have a male and a female terminations on carbmate. Total cost of "DIY rotax adapter" was less than $15

    Hope you have a smooth running engines! Blue skies!

     

      
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