1937 Knuckle motor: Currently 74", is 61" original better?

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  • elvisp1956
    Member
    • Jan 2017
    • 43

    #1

    1937 Knuckle motor: Currently 74", is 61" original better?

    Dilemma; i just bought a 1937 Knuckle motor and it was rebuilt to a 74", but i got the old heads with it (bare). Is it better and worth more if i put it back to original? Or leave it? What would be the right thing to do before building the bike?
  • Chris Haynes
    Curmudgeon
    • Jul 2002
    • 5939

    #2
    The early Knuck cases have been proved to be weak when bumped to 74". What flywheels are in your engine?
    Be sure to visit;
    http://www.vintageamericanmotorcycles.com/main.php
    Be sure to register at the site so you can see large images.
    Also be sure to visit http://www.caimag.com/forum/

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    • Chris Haynes
      Curmudgeon
      • Jul 2002
      • 5939

      #3
      If it still has the 61" flywheels in it and 74" cylinders it is a 68".
      Be sure to visit;
      http://www.vintageamericanmotorcycles.com/main.php
      Be sure to register at the site so you can see large images.
      Also be sure to visit http://www.caimag.com/forum/

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      • elvisp1956
        Member
        • Jan 2017
        • 43

        #4
        I don't know i haven't opened it up...Is there a way to know without taking it apart?

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        • elvisp1956
          Member
          • Jan 2017
          • 43

          #5
          It says 37ELXXXX on the bottom left case and matching belly numbers (original). I also got the frame, tanks speedo, engine rebuilt,tranny and floor boards (all original parts).

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          • Rubone
            Senior Member
            • Aug 2004
            • 4763

            #6
            74 flywheels will not fit into '37 cases unless they are turned down in diameter or the cases were machined out. Neither option is good, the machined case being the worse of the two. Are you sure it is a 74 or does it just have later large port heads on it? If one head is off you can determine engine size easily by measuring bore and total stroke. Does it have 4 fin or 5 fin cylinders?
            Robbie Knight Amca #2736

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            • elvisp1956
              Member
              • Jan 2017
              • 43

              #7
              5 fins, thanks for the help.

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              • Chris Haynes
                Curmudgeon
                • Jul 2002
                • 5939

                #8
                Originally posted by elvisp1956 View Post
                5 fins, thanks for the help.
                With or without the Fire Ring?
                Be sure to visit;
                http://www.vintageamericanmotorcycles.com/main.php
                Be sure to register at the site so you can see large images.
                Also be sure to visit http://www.caimag.com/forum/

                Comment

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