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Thread: H-D Blanked Off Twin Mockup

  1. #1

    H-D Blanked Off Twin Mockup

    Well, I think I've scared up enough parts to build a blanked off 30.5 ci (500cc) single motor for my J racer. I mocked it up using an old set of cases. Hope to start seriously working on it soon. For those who are not familiar with these, it was a common modification used for short track racing back in the teens and twenties. Dale & Matt at WTT have the only remaining factory built complete SCA (single cylinder alcohol) racer known to exist. Many privateers removed either the front or rear cylinder, rod ,etc. from their pocket valve or 8 valve race engines and built blanked off motors to run in the 30.5 ci (500cc) classes.
    Attached Images Attached Images
    Dave Morrill
    Sylacauga, AL. USA.

    Deadly Dave's Blog
    Lost Stories of Early American Motorcycling.

    http://dlmracing.blogspot.com/

    1921 Harley-Davidson Model J Racer

    It will break a hundred, if dropped from an airplane!

  2. #2

    Re: H-D Blanked Off Twin Mockup

    Congrats and good luck.

    When I was in college, my local Indian dealer, Freddie Marsh, had a blanked off Indian racer he campaigned. He offered it to me to buy for something like $500 and, in my great wisdom, I passed and bought a used Honda instead.
    Buzz Kanter
    American Iron Magazine Forum Harley forum
    American Iron Magazine Harley magazine
    Classic Harley Classic Harley Info
    American Iron Magazine Digital Delivery

    "It is always fascinating to watch the development of rationalizations for an argument"


  3. #3

    Re: H-D Blanked Off Twin Mockup

    Seems a waste, unless you are going racing in some vintage class. Are you?

  4. #4

    Re: H-D Blanked Off Twin Mockup

    Wilko,

    My 21J motor has original iron pistons that take rare very wide and hard to find piston rings. The guys that have them, just don't let go of them. I can replace the pistons with more modern aluminum ones, but that involves shipping 89 year old cylinders to a good machinist to get the taper bored out of the cylinders and then fit a modern set of straight bore pistons. They are close to stock bore, so I don't really want to do that right now. I may do that in the future. The parts I'm using are acumulated old spare parts. If it goes up in a little mushroom cloud, it won't be a big lose. I won't race this one, but I may some put some young buck on it if Barber gets a dirt track for old racers. Right now it's just an engineering challenge!:

    By they way, in the late 20s the class was dropped down to 21 ci to again slow the short track bikes down and make the racing safer. Harley released the Peashooter and the blanked twins disappeared.
    Dave Morrill
    Sylacauga, AL. USA.

    Deadly Dave's Blog
    Lost Stories of Early American Motorcycling.

    http://dlmracing.blogspot.com/

    1921 Harley-Davidson Model J Racer

    It will break a hundred, if dropped from an airplane!

  5. #5
    Join Date
    Sep 2008
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    Re: H-D Blanked Off Twin Mockup

    Quote Originally Posted by wilko View Post
    Seems a waste, unless you are going racing in some vintage class. Are you?
    Whad'ya say that for ?

  6. Re: H-D Blanked Off Twin Mockup

    Pretty cool Dave, those old engines are real marvels.

  7. #7
    Join Date
    Nov 2008
    Location
    new britain pa
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    Re: H-D Blanked Off Twin Mockup

    i quess it will only do 50 if drop it from a airplane bring it to wauseon and run the pea gravel.

  8. #8

    Re: H-D Blanked Off Twin Mockup

    More photos of mockup.
    Attached Images Attached Images
    Dave Morrill
    Sylacauga, AL. USA.

    Deadly Dave's Blog
    Lost Stories of Early American Motorcycling.

    http://dlmracing.blogspot.com/

    1921 Harley-Davidson Model J Racer

    It will break a hundred, if dropped from an airplane!

  9. #9
    Join Date
    Nov 2007
    Location
    Puget Sound, America
    Posts
    11,054

    Re: H-D Blanked Off Twin Mockup

    It would be so cool to hear this motor run! Cool stuff, Dave! Thanks for posting, keep us updated.
    52 HydraGlide
    59 Pan/Knuck Chopper
    77 Stroker Shovel FLH
    94 Evo Secret Components

  10. #10

    Re: H-D Blanked Off Twin Mockup

    Quote Originally Posted by Bigincher View Post
    It would be so cool to hear this motor run! Cool stuff, Dave! Thanks for posting, keep us updated.
    Agreed. Dave, once it is up and running you have to load some video of it here.

    Are we going to see that machine on one of the stops for the Motorcycle Cannonball? Hope so.
    Buzz Kanter
    American Iron Magazine Forum Harley forum
    American Iron Magazine Harley magazine
    Classic Harley Classic Harley Info
    American Iron Magazine Digital Delivery

    "It is always fascinating to watch the development of rationalizations for an argument"


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