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23F Frame and Cylinders

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  • 23F Frame and Cylinders

    In a break from the 21F restoration I was having a coffee and looking over the 23F "project" which sits on a wooden stand in the shed.

    The soldered-on piece on the top frame rail in front of the seat post has always been missing, so there is no factory stamping on the frame. In the absence of a code and number, do the following features confirm that it is, in fact, a 23 frame: the attachment of the top tubes behind the seat; the muffler brackets front and rear (still covered in years of road dirt, carbon, oil and what looks like lichen (!); and the rear cylinder brace attachment under the lower of the two top frame rails?

    P1030594 (2).JPG

    P1030589 (2).JPG

    P1030587 (2).JPG

    P1030593 (2).JPG

    The holes for the rear cylinder brace are noticeably more elongated than those on the 21 frame. I'm sure I read somewhere that this was to accommodate the 1923-on cylinders which were fractionally taller than the 17-22 cylinders, and that these taller cylinders were stamped on the base flange. Have I got this right?

    If this is correct, what and where are the stamping marks I should be looking for on my cylinders? A photo would be very helpful. I can't find any marks on the cylinders which are now on the 23 motor but, of course, in the last 98 years the cylinders could well have been replaced.

    As can be seen in the last photo above, the cylinders sit high under the brace bracket but that may be only because they have the compression plates for sidecar use installed

    P1030592 (2)_LI.jpg

    As always, any clarification and information will be much appreciated.

    Mike

  • #2
    Mike
    Yes, that is a mid to end of 1923 frame.
    The marks on the cylinder base flange are found on 74” cylinders only and your motor is a 61” so your cylinders should not have them.
    Mark Masa
    Mark Masa
    www.linkcycles.com

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    • #3
      Thank you Mark. As always, clear, informative and to the point. Do I take it from your post that there is no dimensional difference between 21 and a 23 61" cylinders? And, out of interest, can you point out the difference between an early 23 and a late 23 frame?

      On another matter, I have posted a long-winded question in the "Judging" topic on the forum about what might be a "period correct" Bosch magneto for a 21F motorcycle. In brief, if the 1921 magneto motorcycles were being assembled in the factory in the last half of 1920, then it seems to me that they would be fitted with magnetos made in 1920, and stamped 1920 by Bosch. It may even be possible that some of the early production motorcycles had 1919 magnetos fitted if some of these, left over from the previous year's production, were on the shelf in the factory.

      No replies as yet.

      Thanks again.

      Mike
      Last edited by MikeW; 11-09-2021, 05:55 PM.

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