Float Levels For Concentric Carbs

Discussion in 'Vintage Classics' started by Obijohnkenobe, Jan 7, 2026.

  1. Obijohnkenobe

    Obijohnkenobe Well-Known Member

    Dec 14, 2020
    224
    93
    Tonbridge, Kent, UK
    OK. Have completed a few maintenance tasks on my T100R: Replaced knackered throttle and speedo cables, spotted and replaced almost broken wire between the coils, replaced split rubber boot on clutch cable/gearbox cover, adjusted tappets (all of which had no movement at all (previous owner, not me!), and inspected float levels.

    The floats I happily discovered to be the newer stay-ups, with new alluminium float needles, and new needle jets to boot (why don't people keep evidence of work done!) HOWEVER, the floats were higher than recommended so I lowered them to what they should be. Result, wouldn't start at all. So I re-set the float levels to where they were and she now starts. Either my measuring was rubbish or something else is at play, or maybe the stay up floats do need to be higher than the originals (although Amal dont say so. Any thoughts anyone?
     
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  2. Eldon

    Eldon Crème de la Crème

    Nov 14, 2018
    9,333
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    North Yorkshire
    My only thoughts are, Amal carbs are rubbish compared to Japanese.
    My Armstrong mt500 started life with an Amal as standard fitment but it didn't take long for the various owners of that model to bin them in favour of a Mikuni.
     
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  3. Obijohnkenobe

    Obijohnkenobe Well-Known Member

    Dec 14, 2020
    224
    93
    Tonbridge, Kent, UK
    #3 Obijohnkenobe, Jan 7, 2026
    Last edited: Jan 8, 2026
    Hmm. Good point. I think both Bonnies and Commandos were also often "upgraded" with Mikuni carbs.

    I guess that 50 year old Amals are not exactly "cutting edge".
     
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  4. Iceman

    Iceman Crème de la Crème

    Apr 19, 2020
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    What year is your T100R.
     
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  5. Obijohnkenobe

    Obijohnkenobe Well-Known Member

    Dec 14, 2020
    224
    93
    Tonbridge, Kent, UK
    1972. Unfortunately the carbs don't have the drain plugs at the bottom to facilitate a levelling tube (manometer) to be more accurate with the petrol/float levels, I have to take the bowls off and try and get the levels right that way.
     
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  6. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    1,194
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    appalachia usa
    you can make the amals work if you want to keep them. if you havent already come across it, there may be some extra information here

    https://www.ntnoa.org/pdf/Bushmans Carb Tuning Secrets.pdf

    if you do ever decide to swap to the VM mikunis they will work well. i dont know the initial settings for a T100 but the carbs are easy to tune. TM mikunis have better throttle response, but i have no experience with them.
     
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