when Synchronizing the Carburators (912), the manual and video says that a mechanical synchronization must be the first step in the procedure. The questions I have are:
When you perform the pneumatic Sync by adjusting the wire cover length, I assume that the mechanical sync is no loger valid since the travel of the wire changes. Is that correct?

The last procedure is to adjust the idle. If you adjust the idle at the end of the procedure does it change the peumatico sync at idle?

  • Re: Carburator Synchronization

    by » 13 years ago

    I find that if the sync is roughly correct then there is no requirement to carry out the mechanical sync to start with. I think that the idea of the mechanical sync is just to get the throttles in roughly the correct position before you start.

    The pneumatic balance and idle setting are slightly iterative as one affects the other. When I remove the carbs for service I disconnect the complete throttle linkage from the side of the carb. That way on reassembly everything is in the same place and the balance is maintained.

  • Re: Carburator Synchronization

    by » 13 years ago

    Thnaks Kevin for your comments and nice tips.
    I still have the question about loosing the settings of the mecanical sync when perfoming the pneumatic sync.

    Have you ever accomplished the pneumatic sync on your engine?

  • Re: Carburator Synchronization

    by » 13 years ago

    It is valid when carb's were removed or loosend, the mechanical adjustment is very important to set your carb's for the pneumatic adjustment. If you don't do the mechanical synchronizing both carb's wil be completely out of range to each other and performing the pneumating synchronization will ask to much correction of throttle wires length.

    To adjust the idle at the end, when you found the right idle rpm of your engine bij adjusting the idle stop on your carb's. Just take a feeler gauge of one size and put it between the stop and stop lever of carb bij moving the throttle and check the otherside carb, if distance is the same leave it, if not do adjustment.
    on this way you minimize idle pneumatic difference setting on both carb's

    CAC Holland.nl

    Aircraft mechanic

    Thank you said by: agustin arango, Jez O'Hare

  • Re: Carburator Synchronization

    by » 13 years ago

    Thnaks for your commnents. Lets see if I got it right.
    You are saying that if the carbs are not removed or loosend I don´t always have to perform the mechanical sync?
    or are you saying that mechanilchal sync is always required before a pneumatic sync? In my case the carbs where not removed.

    The second part I think I know what you are saying but can you be a little more specific. When you say "do adjustment" you mean move the Stop screw in the lever until reaching same distance in both carbs? Is the same bolt that was adjusted during the mechanical sync?

    Thanks for your patience

  • Re: Carburator Synchronization

    by » 13 years ago

    The mechanical adjustment is only necessary when the carbs or throttle cables have been removed and replaced for some reason. It is just to get you fairly close before the pneumatic balancing. Once the pneumatic balancing is done, The throttle lever should not touch the throttle stops on the carb either at idle or full throttle. Throttle movement is then limited by the throttle stops on the throttle quadrant itself. Reason for this is that any excessive force exerted by the pilot is absorbed at the throttle quadrant and not by the cable, or splitter, or carb stops.

    Hope this helps,


    Thank you said by: agustin arango

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