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Finding TDC on 439

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  • Finding TDC on 439

    I'm embarrassed to ask this question, but I'm stumped. I want to determine TDC for my engine. Manual says to put a stiff wire in the #1 plug hole. This is standard procedure and I actually use a dial indicator and a degree wheel to determine exact TDC. But with the config of the flathead, I cannot use an indicator and from what I can see thru the plug hole with a flashlight, not confident that you can get an accurate reading with a "piece of stiff wire" per the manual.

    I don't want to pull the timing cover as I just got it to stop leaking. I see no other port on the block that lets me see a mark on the flywheel or similar.

    I had the distributor off because it was not positioned right relative to the cut-out relay. So when I could not figure out how to find TDC, I simply used the points to tell me because the engine was running fine.

    Maybe that's close enough given it is a manual spark engine. Irv Truax said the engine should not idle smoothly when fully retarded and should lope. Mine did not lope and I found my points were set about 0.009". Manual said 0.020" so I suspect the cam follower on the points had worn and closed up the points. That should have retarded the spark, but it was definiately not overly retarded. Ran very smooth at fully retarded position.

    But I digress. Is there a trick for finding TDC on these engines?

    Thanks and regards,
    Rob
    Regards,
    Rob Sigond
    AMCA # 1811

  • #2
    Rob!

    Make a 14mm fitting from a destroyed plug, and attach a very small clear vinyl tube.
    Then, when installed in a plug hole, a drop of oil in the tube will rise and fall with the cylinder's piston, and TDC will be its highest travel.

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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    • #3
      I just did this on my 22JD. Just use a dial indicator with an extension post though the plug hole. Piston hits post. Job done.

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      • #4
        That's a great idea. Someone mentioned using a balloon in a similar fashion. But the oil in the tube is simplicity at it's finest.

        What I like is I should be able to use a long piece of tubing and run it over to the other side of the bike. I use a strap wrench or just my hand on the generator coupling to turn the engine over. So with the tube on that side, I can watch it. That was my real challenge, figuring out how to see whatever indicator solution that I could use and see it from the left side of the bike. I currently have no way to raise the rear end off the ground and turn the engine with the rear wheel.

        Thanks,

        Rob
        Last edited by Snakeoil; 06-20-2013, 09:39 PM.
        Regards,
        Rob Sigond
        AMCA # 1811

        Comment


        • #5
          Originally posted by Robert Luland View Post
          I just did this on my 22JD. Just use a dial indicator with an extension post though the plug hole. Piston hits post. Job done.
          I don't think that will work on this engine with the intake over exhause valve arrangement. I guess if you knew you were near TDC you would be okay. But I'm doubtful there is room when the valve comes down. It partially covers the plug hole.

          Thanks just the same.

          Regards,
          Rob
          Regards,
          Rob Sigond
          AMCA # 1811

          Comment

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