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Hodgson Radial 9 cyl.

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  • Hodgson Radial 9 cyl.

    I need help.

    I have completed buiding the Hodgson 9 cyl radial. Terry Mayhugh's thread was tremendous help. Unfortunately, mine barely runs. I will go over the basics I have:
    1. Using Perry 4600 carb, as recommended by Lee Hodgson.
    2. S/S CDI ignition.
    3. Compression is fair at 50 - 60 PSI.
    4. Valve timing has been checked and rechecked.
    5. Ignition timing 10 Deg advance.
    6. Oil flow is controlled.
    7. Engine is getting fuel.
    8. Spark is strong. Plug gap at .020". NGK CM6 spark plugs.
    9. No air leaks. I pressurized intake system to verify.
    10. I have tried gasoline and camp fuel.

    When it does run, it hits on only 4 or 5 cylinders. Not always the same cylinders on different runs.

    I am at the end of my rope on this. Any help would be greatly appreciated.

    Regards,
    Jon

  • #2
    If everything has been checked, maybe vibration during the run is causing issues?

    Comment


    • #3
      Is this the same as the Ageless engine?
      the plans come from Cincinnati?

      Comment


      • #4
        Not a ton of compression, but lots of Briggs' run with only a little more. Is that measured or calculated?

        How do you know you have reasonable fuel distribution? There are a lot of cylinders to supply, and mixture has to flow up as well as down. You could have over rich lower cylinders, over lean upper, and be running only on some of the middle ones.

        The inconsistent running sounds much like fuel issues, that is the simplest reason. The other possibilities are mechanical issues that do not seem as though they ought to cause that.

        What is the compression supposed to be?

        If measured, I'd think with the small cylinders you might have trouble measuring, and if calculated, it ought to come out to what the plans say, unless there is a mistake in construction. If that is measured value, it seems the real value might easily be 20 to 30% higher actually, due to the problems of measuring.
        2730

        Keep eye on ball.
        Hashim Khan

        Everything not impossible is compulsory

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        • #5
          I'm no help on radial engines, but from my experience as an auto mechanic. When everything seems like it's right but the engine just doesn't run, it was usually a signal to me that there was an incorrect assumption somewhere. The distributor was timed for TDC exhaust rather than compression. The timing was checked when the points were closing, not opening. A friend told of a frustrated mechanic he knew who was working unsuccessfully on some car. He said, "It's got gas, it's got air, it's got spark. It has to run, it doesn't have any choice". Well, it did have a choice.

          If I recall from Brian Rupnow's experience with his small engines, sometimes he'd spin them with an external motor for a while to break in components, particularly rings and valves to get compression up.
          .
          "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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          • #6
            Thanks for your thoughts. I believe the problem is arcing somewhere in the distributor. I haven't solved it yet.
            Any more suggestions would be welcome.
            Jon

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            • #7
              Because of the firing order, single row radials run rough sounding at idle under normal conditions.

              On full size engines it is quite common for the spark plugs on the lower cylinders to oil foul when sitting. Oil in the crankcase drains down past the rings. This is why it's so important to rotate the engine slowly by hand before starting to check against oil hydro-locking a bottom cylinder. Be sure your plugs are clean before starting the engine.

              Did you spin the engine for any length of time without the plugs installed? Not only the rings, but the valves might need a little breaking in too. They might seal fine when stationary yet hang up a bit at operating speeds.

              Comment


              • #8
                Just for kicks, why not try a shot of starting fluid and see if it'll light off on that?

                You might try warming the engine as much as possible to give it some help. Put it in a box to hold as much heat as possible and use a heat gun or hair dryer. A warm engine will fire up more easily than a cold one.

                Is 60 PSI in the ballpark for a similar engine?

                This thing needs to run. And we need feelthy veedeeos!

                Comment


                • #9
                  Is the firing order correct?

                  Are you sure that it is 10* advanced and not retarded?

                  -Bob

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                  • #10
                    That's a good thought. I can sometimes feel a slight backward kick when rotating by hand, so that tells me it is advanced.
                    Jon

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                    • #11
                      Jon-

                      How did you determine tdc? Did you use a piston stop and a degree wheel?

                      An old school timing light will work with a S/S ignition if you engrave timing marks. (At least on my single cylinder "Tiny".)

                      -Bob

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                      • #12
                        Bob,
                        I used a dial indicator on top of the piston and a degree wheel. Set the crank to 10 Deg advanced and rotate the distributor until the spark plug fires. Confirm by rotating the crank and observing the degrees of when the plug fires.

                        Pretty much the way I timed the old Model A Ford when I was a kid. I'm not really that old! The Model A was a '29, and we bought it in the sixties to play with.

                        Regards,
                        Jon


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                        • #13
                          Jon-

                          You used a sound method to set initial timing. I know from experience with my "Tiny" that the S/S ignition will find an alternate route if the plug is slightly fouled. Have you examined the distributor cap under magnification looking for any carbon trails?

                          -Bob

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                          • #14
                            What material did you use to make the distributor cap?

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                            • #15
                              I have looked for tracking in the cap, and can find no sign of it. Just to be sure, I went over the inside of the cap with a wire brush in the Dremel tool.

                              i am using Acetal for the cap and rotor from McMaster Carr.

                              Amazingly, on the bench, I was able to pass a spark through .175" in of acetal. I would not have believed it had I not seen it with my own eyes.
                              Jon

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