How to measure a Guzzi headlight ?????

Discussion in 'Old's Cool' started by Nitram, Feb 13, 2014.

  1. Nitram

    Nitram Been here awhile

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    I'm trying to track down a replacement CEV headlight rim and glass for my 1956 Guzzi Lodola. There are rims for sale on fleaBay, but what I'm not sure about what they mean when they say e.g. that they have a 150mm headlight rim. Is that the size of the o.d. of the lip on the headlight bucket ? Like this:
    [​IMG]
    Or is it the diameter of the headlight glass ? Or the O.D. of the rim itself ?
    Any thought ?
    Ta
    Nitram
    #1
  2. goatroper

    goatroper Been here awhile

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    I am not an authority but with CEV (or APRILIA) headlights there are not that many sizes, maybe 150, 130 and 105mm. Roughly 6, 5 and 4 inches across the opening respectively. Your photo shows a 150 as you suspected.
    Hope this helps.
    #2
  3. DesmoDog

    DesmoDog Desmo's my dog

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    No, the rim measures 150 but that's not where the sizes listed on trim rings comes from. It's been a couple years since I played around with these but IIRC the listed size is the lens, not the shell. In any case, a "150" headlight has a shell OD the measures more than 150mm. If I had to bet I'd guess that shell takes a 130mm trim ring.

    I'll measure one of each when I get home to give examples... I've forgotten what they were now but if I were to guess I'd say a 150mm shell measures about 168mm where the trim ring fits on?

    Also, not all 150mm trim rings fit all 150mm shells, even within the same brand. Or so I was told when the 150mm trim ring didn't fit the 150mm shell I bought to go with it...
    #3
  4. DesmoDog

    DesmoDog Desmo's my dog

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    Here is an Aprillia "150mm" headlight shell

    [​IMG]

    Here is an Aprilia trim ring (reproduction)
    [​IMG]

    It fits much too loosely on that shell, but I've been told it may fit a different style Aprilia 150mm shell.

    You need a 130mm trim ring for the shell you'v shown IMHO.
    #4
  5. England-Kev

    England-Kev Long timer

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    The original post shows a headlight bucket for a 150mm glass, so you need a 150mm rim to go with it, six inches , in old money.:evil
    #5
  6. DesmoDog

    DesmoDog Desmo's my dog

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    The original photo shows ~150mm dia for the mounting surface of the shell.
    As the pictures of the trim rings show, the glass is not the same diameter as the mounting flange. A 150mm lens will be too big for that shell.

    Here are photos of a 130mm CEV trim ring. Says so right on it.
    [​IMG]

    Here's the dimension of the ring where it fits the shell.
    [​IMG]

    That shot also shows that the glass is not the same size diameter as the mounting surface. A "130mm" trim ring fits on a shell that's about 150mm in diameter. That shell is NOT for a "150mm" headlight.
    #6
  7. goatroper

    goatroper Been here awhile

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    DesmoDog is correct. The 105, 130 or 150 mm seems to refer to the headlight not the bucket, so the bucket and rim must be larger.
    #7
  8. Nitram

    Nitram Been here awhile

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    Thanks folks.
    It seems pretty clear that for my headlight bucket, I need a 130mm ring and glass. They are around on ebay I think, so it shouldn't be too hard.
    Thanks again for taking the time to respond to my question.
    Cheers,
    Nitram :-)
    #8
  9. MZRider

    MZRider Neo-Luddite

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