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What does the Jet Size Indicate ?
  • topgun
    Posts:511
    Joined:Wed Aug 30, 2006 8:27 pm
    What does the Jet Size Indicate ?

    by topgun » Thu Apr 12, 2007 2:56 am

    Ok here's one for the brain's trust ...

    What does the Jet Size indicate ? I know it is not the physical size of the "hole" in the jet

    I think it relates to the amount of fuel that flows through the jst in a given time period ??

    Just curious ...

    Anyone with a definitive answer ?
  • Aussiecrf230
    Posts:1964
    Joined:Fri Jan 06, 2006 11:11 pm

    by Aussiecrf230 » Thu Apr 12, 2007 3:29 am

    Generally it is the hole size in millimetres, but I know for a fact some carb manufactures(cars at least) numbers refer to flow rates.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas
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    mustang
    Posts:255
    Joined:Fri Jul 15, 2005 4:12 pm

    Re: What does the Jet Size Indicate ?

    by mustang » Thu Apr 12, 2007 5:56 am

    topgun wrote:Ok here's one for the brain's trust ...

    What does the Jet Size indicate ? I know it is not the physical size of the "hole" in the jet

    I think it relates to the amount of fuel that flows through the jst in a given time period ??

    Just curious ...

    Anyone with a definitive answer ?

    The numbers on the jets are the size of the hole thru it .

    A main jet that is 100 =1 mm hole
    200 = 2 mm 175 = 1.75 mm etc. , etc.
    pilot jets are the same 42 pilot =.42 mm
    c-ya****mustang Image
  • topgun
    Posts:511
    Joined:Wed Aug 30, 2006 8:27 pm

    by topgun » Fri Apr 13, 2007 1:49 am

    Mustang

    Not doubting your answer but are you sure on that ? - OK so I am a little skectical ...


    Checked some old Mikuni jets I have and no way would a 1 mm drill bit fit thru a # 100 main jet so that led me to theory of flow rate ...
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    Crazy_Steve
    Posts:159
    Joined:Thu Mar 02, 2006 4:20 pm

    by Crazy_Steve » Fri Apr 13, 2007 2:01 am

    topgun wrote:Mustang

    Not doubting your answer but are you sure on that ? - OK so I am a little skectical ...


    Checked some old Mikuni jets I have and no way would a 1 mm drill bit fit thru a # 100 main jet so that led me to theory of flow rate ...


    He's right.

    And the Honda's carb is a Keihin.
    he back.
  • topgun
    Posts:511
    Joined:Wed Aug 30, 2006 8:27 pm

    by topgun » Fri Apr 13, 2007 2:13 am

    Ok .... yes I am aware of the carbs Honda use :D

    But do all manufacturers use the same method to size jets ?

    Tried Googling it but no real answers to be had ..

    So I am trying the definitive source ... you guys !!!

    And yes I am not being very receptive to your answers which is very rude of me so I apologise ....
  • Asmith
    Posts:14381
    Joined:Mon Apr 10, 2006 7:52 am

    by Asmith » Fri Apr 13, 2007 7:05 am

    topgun wrote:So I am trying the definitive source ... you guys !!!



    I think I found the error in your thinking... :lol:
  • topgun
    Posts:511
    Joined:Wed Aug 30, 2006 8:27 pm

    by topgun » Fri Apr 13, 2007 5:13 pm

    OIC .... my bad ...

    :D
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    nminus1
    Posts:3613
    Joined:Mon May 01, 2006 11:16 am

    by nminus1 » Fri Apr 27, 2007 7:52 pm

    I believe Mikuni uses flow rate, Keihin uses size. Ex Mikuni 100 = 100cc per minute. However this is further complicated as I dont know what psi they are measuring at, I bet at 500 psi it would be more like a litre per minute, must be a nominal value used. I bet some smart M.E. aka AS would know....
  • Aussiecrf230
    Posts:1964
    Joined:Fri Jan 06, 2006 11:11 pm

    by Aussiecrf230 » Sun Apr 29, 2007 6:12 am

    The standards for flowing heads is a either a vacuum of 10 or 25 inches of water.

    For some reason I think small items were done at 2 inches but I would have to check.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas
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