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Thread: Knuckle Jug Date Codes

  1. #1
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    Default Knuckle Jug Date Codes

    My VIN is EL401607 ... an early production 1940 EL. I have a couple of cylinders with date codes of 19 - 9, and 21 - 9. I assume these are 1939 codes, but don't know what the two digits before the dash represent. Are these month and day, or something else. I'm trying to determine if these are compatible with my engine production date.

    A related question I'll ask here, rather than on a separate thread is when did production typically begin for a model year (recognizing that it may have changed over time, or even from year to year)? Further, what kind of lead time would there be between the manufacture of significant components (e.g., heads, jugs, transmissions, fly-wheels, etc.) and the motorcycle assembly. I am relatively new to old Harleys, and come from more of a Corvette restoration background where all of this info is readily available ... so I recognize that I may be asking questions without answers, or the answer may not make a difference with these bikes.

    Thanks.

  2. #2
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    Default

    The 19 and 21 are probably days of the month. In front of the this or around the corner on the flange should be a letter that represents the month. 1940 is the first year of the 5 fin cylinders so your cylinders would be right if they had 5 fins.

    Jerry

  3. #3
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    Default

    You should notice a large letter casting. Often around the corner from the numbers. So lets say you letter is "H". Sometimes this letter is upside down. So the casting would read H 19 9
    H is the eight letter of the alphabet, making it the eighth month or August. The 19 is the day and 9 is the year, 9=39 in this case. I am sure you could tell the difference between a 1939 or 1949 jug.
    So the jugs would have been cast Aug/19/39. Model year change is usually in June so jugs cast in Aug of 39 would be for a 1940 model machine.
    See how it works? BTW the letter "I" was usually, but not always, skipped as not to be confused with a number "1".
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  4. #4
    Join Date
    Nov 2001
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    Chris.
    Do you know how to date early 4 fin cylinders?

    The system for dating cylinders you describe works for a 1940 model machine but it will not work on early 4 fin cylinders?

    Early cylinders did not have the large letter casting (For the month) and the number plate was nailed on not screwed on. Some examples of numbers I have seen are
    11-22 12-11 22-10 12-13. None of these will work if using the code you describe?

    Later 4 fin cylinders had the large cast in letter and the number plate was screwed on not nailed. All the examples of this type that I have seen have the large letter next to the number plate, the code works on all the examples of this type that I have recorded.
    The earliest of this type I have seen is C 29-8 so this jug would have been cast on the 29th march 1938.

    It would be good to find out how to date the early cylinders and it would be interesting to know when the month letter casting and screw on number plates started.

    Pete.

  5. #5
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    I haven't found anybody who can tell me about the early cast codes. I got the information on the later codes from Motor Masting Company who cast the cylinders and head for H-D. That is their trademark logo on the heads and jugs.
    I have very early four fin jugs with no cast code on them and one with an EX number on it.
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  6. #6
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    Mar 2008
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    Thanks Chris,

    In answering one question, you may also have answered another that I have yet to get a good answer on ... model year changeover. Was June typically the model year changeover? I would've guessed Sept - Oct. The reason this is important to me is that given my serial number, I would've thought a late 1939 date code would be appropriate. If the model year changeover was typically in June, however, maybe a mid-year date code would be best. My transmission is not original to my bike, but my engine, frame, heads, springer, cylinders are consistent. It seems that if we knew typical monthly production and model-year changeover, we could reasonably estimate the "birth-month" of our bikes. I am assuming that production was steady in most months, with exceptions for strikes, summer months, model-year changeover, etc. But if we know total annual production, and divide by 10 or 12, we can estimate monthly production, and then add this to the model-year changeover month.

    I know this may sound a little anal (and isnt't that part of our hobby), but this would then give us some consistency when attempting to replace an incorrect part with a correct part, or identifying a part that is more likely than not original to a particular bike. Any idea if any of this information is available somewhere? Given my 1607 serial number, and the fact that serial numbers began at 1000, my bike is a pretty early production.

    Thanks,
    Vic

  7. #7
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    My original '47 EL has a 14000 range SN. The rear jug, which happens to be sitting on my desk in front of me has a date code of F-2-7 if that helps anyone. That would make it a June manufactured jug and my bike was near the end of the run for that model year.

    I had to replace my rear jug. I found a NOS jug with a 1949 casting date. Henke said this would be fine since it would be feasible for a bike to have a later jug from a rebuild. The reverse is also feasible since a dealer could have had an older dated jug on his shelf for spares and used it to rebuild a later model. I was just happy to find a NOS jug.
    Rob Sigond
    AMCA # 1811

  8. #8
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    Quote Originally Posted by Snakeoil View Post
    I had to replace my rear jug. I found a NOS jug with a 1949 casting date. Henke said this would be fine since it would be feasible for a bike to have a later jug from a rebuild. The reverse is also feasible since a dealer could have had an older dated jug on his shelf for spares and used it to rebuild a later model. I was just happy to find a NOS jug.
    Sure it will be fine, untill you find a judge who needs to nit pick.
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  9. #9

    Default Huhhh

    Chris and all....


    ""Sure it will be fine, untill you find a judge who needs to nit pick"".


    This is an example of the reason why I will never have a bike that I own judged/appraised.

    George
    George Greer
    AMCA # 3370

  10. #10
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    Jul 2001
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    Quote Originally Posted by George Greer View Post
    Chris and all....


    ""Sure it will be fine, untill you find a judge who needs to nit pick"".


    This is an example of the reason why I will never have a bike that I own judged/appraised.

    George
    George
    if the only thing the judges could find wrong was a 1/4 point for one cylinder with a wrong date code,that is not nit picking. that is one BEAUTIFUL BIKE!!!
    Kevin Valentine 13
    EX-Chief Judge

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