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Thread: harley 10/12

  1. harley 10/12

    G,day i am trying to get info on the Harley 10/12 is this a ulh not real sure 80 cubic? cheers Rob.

  2. #2
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    Re: harley 10/12

    The term is Oz and refers to the RAC (Pommy) rated horsepower used for registration purposes. The formula is a combination of bore and stroke. 10/12s are "Big Twin" in U, UL and ULH. U was 74cu UL was 80 cu and ULH the same with higher comp heads.

  3. Re: harley 10/12

    Purri,thanks i wasnt sure if the vld or any 1200 cc jd etc came into that 10/12 also, cheers Rob

  4. #4
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    Re: harley 10/12

    "VLH" was the 1935 and '36 80" model's designation, if that helps. U's with 13 fins down the left side of the cylinder are 80s, unless 1937, when 74s (U's and higher comp UL's) and (UH's and ULH's, the 80s) both ran 13 fin cylinders: 120-37 front and 120-371 rear.

    Don't know if this helps, since you guys are talking Ozzie registration nomenclature, but a UL is a 74, just higher comp. "H" makes it an 80": UH, low and ULH, high comp. (using M51L carburettors, both)
    Last edited by Sarge; 04-12-2012 at 01:44 AM.
    Sarge, Gerry Lyons, Fla.
    F.O.G. member: http://flatheadownersgroup.com/
    www.37UL.com
    "It's a 1937, and the downside is, it's out of warranty"

  5. #5

    Re: harley 10/12

    Quote Originally Posted by purri View Post
    The term is Oz and refers to the RAC (Pommy) rated horsepower used for registration purposes. The formula is a combination of bore and stroke. 10/12s are "Big Twin" in U, UL and ULH. U was 74cu UL was 80 cu and ULH the same with higher comp heads.
    Actually the U was the 74" Solo Medium Compression. The UL was 74" Special Sport Solo, and the ULH was the 80" Special Sport Solo.
    Chris Haynes
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  6. #6

    Re: harley 10/12

    And don't forget the UH, 80" solo medium compression!
    Robbie

  7. #7
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    Re: harley 10/12

    Rob, I remember here in West Aust abouty forty years ago that people referred to a U-series Flathead as a 10/12 and something like a WLA was referred to as a 6/7. And I think (not sure) something like a 61ci F-head was referred to as a 7/9.
    Eric

  8. #8

    Re: harley 10/12

    In the US the licensing data was different and used the N.A.C.C. system for horsepower ratings. As you see here in the riders handbooks they show both types of commonly used ratings in the US.
    Robbie

  9. Re: harley 10/12

    Eric,thanks for your imput ,i throughout american mates used this term also 10/12 ,i have only ever known this term for the big twins ,not knowing that these where u,ul,ulh ,you mention the 6/7 and 7/9,i have not heard of these terms before,i had words with an old copper on the gypsy tour a few years ago i was on my 22 chief and he swear black n blue that my 1000cc chief was a 10/12 ,he did not listen to me but i let him have his say he was an old police bike copper in his early 80s .

  10. #10
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    Re: harley 10/12

    I contacted one of my mates who is a member of the Vintage Motor Cycle Club here and he said most of the older (75yo +) club members use the three terms I mentioned earlier: 10/12; 6/7; and 7/9. And he recalls seeing some very old rego papers in which it referred to a bike being a 7/9. He’s always taken these terms to be the horsepower rating (category) used by the police for West Aust registration purposes although he’s not positive about that.
    Eric

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