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Thread: Setting up Timing on a JD

  1. #1

    Setting up Timing on a JD

    Hey Folks

    I'm about ready to start my JDH, but need help with the timing. I have a Joe Hunt Maggy into a std generator using an adapter made by Randall Cox (who I've just found out Passed away in 2014 RIP)
    All Help greatly appreciated!

    cheers & beers
    Laurie
    A good friend will come and bail you out of jail.....
    But a true friend will be sitting next to you saying...
    Damn we screwed up!

  2. #2

    Re: Setting up Timing on a JD

    I have the same configuration on my JDH.
    This was the procedure used for my two-cam racer (4 3/4 stroke =
    128,7 millimetres), but it at the "longest end" of the tolerance
    (i.e. the longest distance) for measure given before top centre
    (measure through the upper hole for the top engine mounting holes)
    given for any "H" motor.

    Measure was 13/32 = 10.3 millimetres, the Bosch ZEVs are marked "I"
    for front cylinder and "II" for rear cylinder.

    Thus, (1) assure that the cylinder in question is on ignition stroke
    (coming up to be ignited) while having inserted all cam gears in the
    cam chest according to theirs' respective marks - except the gear to
    the magneto. (2) turn the magneto until it just opens for the
    particular cylinder and finally (3) insert the gear to the magneto.

    https://youtu.be/_Xv2EdMIPss

  3. #3

    Re: Setting up Timing on a JD

    Eric
    So is it 10.3mm BTDC on the front cyl, then set the points to just open and insert the gear to generator? what is the easiest way to measure BTDC? as the motor is in the frame




    QUOTE=2cam;287055]I have the same configuration on my JDH.

    This was the procedure used for my two-cam racer (4 3/4 stroke =
    128,7 millimetres), but it at the "longest end" of the tolerance
    (i.e. the longest distance) for measure given before top centre
    (measure through the upper hole for the top engine mounting holes)
    given for any "H" motor.

    Measure was 13/32 = 10.3 millimetres, the Bosch ZEVs are marked "I"
    for front cylinder and "II" for rear cylinder.

    Thus, (1) assure that the cylinder in question is on ignition stroke
    (coming up to be ignited) while having inserted all cam gears in the
    cam chest according to theirs' respective marks - except the gear to
    the magneto. (2) turn the magneto until it just opens for the
    particular cylinder and finally (3) insert the gear to the magneto.

    https://youtu.be/_Xv2EdMIPss[/QUOTE]
    A good friend will come and bail you out of jail.....
    But a true friend will be sitting next to you saying...
    Damn we screwed up!

  4. #4
    Join Date
    Nov 2008
    Location
    new britain pa
    Posts
    3,239

    Re: Setting up Timing on a JD

    Easiest way would be X-ray. But that’s not really gonna happen. Remove your top cylinder plug. You can drop a plastic drinking straw down onto your piston. Don’t let go until you feel it touch the piston. Find tdc. Mark it then rotate motor backwards to your need distance. It’s all you got or remove your motor

  5. #5

    Re: Setting up Timing on a JD

    Yeah thanks rob

  6. #6
    Join Date
    Feb 2011
    Location
    Sarasota, Florida
    Posts
    6,258

    Re: Setting up Timing on a JD

    I drilled a 1/8" hole in the top motor mount studs on my '16 so I could use short 1/8" steel rods to find find TDC, and .312" BTDC. I drilled and tapped the hole in the studs to accept a 10-32 button head screw and gasket so I could seal the hole. It's a tight squeeze to get the rod into the rear stud hole with the motor in the frame, but it can be done. Harley-Davidson should have made a provision for their mechanics to find piston location with the motor in the frame, but apparently that wasn't a priority

  7. #7

    Re: Setting up Timing on a JD

    Thanks Rob, will let you know how it goes. While I got your attention how much oil do I put into the engine and what's the procedure, turn it over to get oil pressure? how do I check oil pressure? so I gather I can start and run it with just the oil in the crank cases? and no oil tank connected? sorry for the dumb questions but this is my first J and I want to get it right.
    cheers & beers
    Laurie
    Quote Originally Posted by rob View Post
    Easiest way would be X-ray. But that’s not really gonna happen. Remove your top cylinder plug. You can drop a plastic drinking straw down onto your piston. Don’t let go until you feel it touch the piston. Find tdc. Mark it then rotate motor backwards to your need distance. It’s all you got or remove your motor
    A good friend will come and bail you out of jail.....
    But a true friend will be sitting next to you saying...
    Damn we screwed up!

  8. #8

    Re: Setting up Timing on a JD

    Quote Originally Posted by dingo View Post
    Thanks Rob, will let you know how it goes. While I got your attention how much oil do I put into the engine and what's the procedure, turn it over to get oil pressure? how do I check oil pressure? so I gather I can start and run it with just the oil in the crank cases? and no oil tank connected? sorry for the dumb questions but this is my first J and I want to get it right.
    cheers & beers
    Laurie
    Dingo! Congrats on having a 2 cam as your first J! What a challenge, it's hard as heck to do it in America. The added geographical challenge can't make it easier.

    The starting procedure on a J is pretty easy. 3 pumps of oil with the hand pump, kick it a few times with the ignition off to spread it around a bit, choke retard and kick. Should pop right off if your timing is anywhere near correct. I wouldn't worry about an oil tank or a feeder if you have oil rings as the oil won't really burn out. I actually have issues where it just keeps accumulating so I've almost shut my feeder off completely.

    If it runs poor, it's usually the timing and a bit of carb tuning coupled with air leaks at the intake. Otherwise if everything is spot on it'll run nice. The J really gives a lot of feedback to poor tuning.... At least mine does.

    I take pictures of the gear train at 1/16 intervals BTDC for timing increments so I don't have to keep pulling the tanks off to adjust timing. Just control the gear lash. Then it's just adjusting the mag gear to the proper point opening location.

    Hope this helps.
    27 JD (almost)

  9. #9
    Join Date
    Nov 2008
    Location
    new britain pa
    Posts
    3,239

    Re: Setting up Timing on a JD

    Bright now there is a good thread on the amca forum about jd oiling . I don’t know how to post a link from my phone or I would. It will answer your oil questions

  10. #10

    Re: Setting up Timing on a JD

    Rob
    Just read the post on AMCA site, just what I needed to know
    Cheers mate
    Quote Originally Posted by rob View Post
    Bright now there is a good thread on the amca forum about jd oiling . I don’t know how to post a link from my phone or I would. It will answer your oil questions
    A good friend will come and bail you out of jail.....
    But a true friend will be sitting next to you saying...
    Damn we screwed up!

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