Primer vs Choke - ROTAX 503, dual Carb.

Discussion in '2-Stroke Aircaft Engines' started by Tuneturkey, Oct 5, 2019.

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  1. Oct 5, 2019 #1

    Tuneturkey

    Tuneturkey

    Tuneturkey

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    For operation in the sunny south, Is a choke really needed, or is a primer to both carbs sufficient?
    Is it possible to siphon fuel from one carb to the other thru the primer tubing? Will balancing the carbs prevent this from happening? Are check valves available to insert in the 1/8" tubing to prevent siphoning?
    Thanks
     
  2. Oct 5, 2019 #2

    poormansairforce

    poormansairforce

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    I used a primer on my 340 and Hirth and never used the choke. Didn't worry about siphoning. Started on the second pull every time.
     
  3. Oct 6, 2019 #3

    MadProfessor8138

    MadProfessor8138

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    No choke required if you use a primer...no matter what the temp is.

    Kevin
     
  4. Oct 6, 2019 #4

    Dana

    Dana

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    Don't the Bing carbs all have an enrichener (which is effectively the same as a choke) already?
     
  5. Oct 6, 2019 #5

    radfordc

    radfordc

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    They do, but I find that using just a pump primer works better. There is no chance of siphoning of fuel between carbs; check valve is not needed.
     
  6. Oct 6, 2019 #6

    MadProfessor8138

    MadProfessor8138

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    I've seen a few different setups with the Bing carbs.
    Choke system and no choke at all....if I remember correctly.
    Not sure of carb models etc.....Armilite would be a better source of info on that topic than me.

    I do know that you should never need to use a choke if you have a primer system installed.
    Once the engine fires from the fuel prime it will stay running.

    Kevin
     
  7. Oct 6, 2019 #7

    Dana

    Dana

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    I added a primer when I had a Cuyuna and it's the way to go, but the enrichener also is useful... it can help to keep it running while it warms up, and is a good diagnostic tool... if you suspect lean running, pull the enrichener, if the rpms increase it was indeed too lean.
     

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