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New Points Ignition, Kill Switch and Crank Position Indicator


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  • New Points Ignition, Kill Switch and Crank Position Indicator

    Hey folks,

    Hope everyone’s doing well. Apologies, very long post to follow.


    - The Dyna ignition died in my ’80 FLH 80, replaced it with points, working great.
    - I installed a stock kill switch; off position powers a crank position indicator circuit to tell me when to kick start.
    - Short flash = front cylinder spark. Long flash = rear cylinder spark. Kick start on the next compression stroke after the long flash/before the front cylinder fires.

    The long part:

    Last summer the Dyna S ignition on my stripped 1980 FLH 80 died; ran the Dynatek diagnostics on the 6.5 yo unit and it was indeed toast. Instead of mindlessly replacing the unit, I decided to install some points and see how that worked. Bottom line, it’s working great, but not without some effort.

    As noted by others earlier, the points cam in the Drag Specialties unit I got was off by 10-15 (?) deg; had to expand the notches in the base plate to get the engine timed and running right. Why are they making the cam like that? Anyway, Jim’s great post here re points set-up and timing made set-up a breeze. Added benefit seems to be the static timing has the bike much easier to kick start. Added kudos go to Dave at Dave’s Cycles in ABQ; out there on business he told me a few things I ought to change, too: metal core plug wires, Champion N12YC plugs, gapped to 0.030” (not 0.040 spec’d for electronic ignition).

    Dave also sold me a used kill switch faceplate. I installed the switch in the stock position on the right handlebar, got tired of reaching down below the left gas tank to turn the ignition switch. The stock kill switch mounts in a housing that’s part of the front master cylinder assembly. Only one throw of the SPDT lever switch is used to control B+ to the coil primary; I’m using the stop position throw to power a crank position circuit. I’ve been wanting to gin up this thing for years, but couldn’t figure an easy way to mount a Hall effect sensor inside the cone cover w/o drilling through the cover, through the wet, etc. The points ignition, Jim’s test light timing procedure and the new kill switch enabled me to implement the crank position circuit.

    The stock kill switch housing has two momentary switches below the switch that normally control the starter solenoid and right turn signals; I use neither on my bike. I have a manual lever solenoid attached to the bendix gear that eliminates possible binding and lock-up sometimes seen on misaligned starter set-ups; this malady causes the starter to keep running, even with key off, until the starter motor burns up or the battery drains. I installed the lever solenoid and a B- cutoff switch years ago to eliminate this possibility. My bike has no turn signals, hand signals are still legal in VA (though not in all states). I’m using the holes for these two switches to mount LEDs for the crank position circuit, described below.

    The kill switch works like a champ, just have to remember to switch it back up to the Run position while starting, either by the starter motor or kicker.

    At this point you may be wondering why I need a crank position indicator at all; the answer is simply to let me know the correct time when to kick start the bike.

    A little background, sorry, everyone here knows this, but I had to think about this to get my mind right. The connecting rods in Harley’s 45 deg V-twins share the same crankpin, resulting in the front cylinder firing, 360o – 45o or 315o crank degrees later the rear cylinder fires, then 360o + 45o or 405o later the front fires again. This uneven 315o-405o-315o duration between firing is responsible for Harley’s characteristic uneven sound. Here’s the key: If you try to kick on the compression stroke of the rear cylinder, it’ll never start because even if it fires, there isn’t enough momentum/rotational inertia to keep the motor turning through that 405o before it gets to the front cylinder. You must kick on the front cylinder compression stroke; if it fires there’s enough momentum to turn the motor 315o before the rear cylinder fires and away it goes, the engine starts.

    Click image for larger version

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    Old timers/real bikers who I’ve spoken with about this idea say I’m just a puss and should simply “feel” for the correct compression stroke when kicking the bike over, as Harley riders have had to do for time immemorial. That’s fine, but I’d still like to have an indication whether I’m kicking at the right time or wasting my time.

    The points cam provides a convenient method for discerning which cylinder is firing. The cam is roughly wedge-shaped; the pointed end opens the points at the front cylinder firing position for a short duration, while the wide back end of the cam opens the points at the rear cylinder firing position for a longer duration. With the kill switch in the stopped position, the points provide a means for activating a pair of LEDs when the points are open and turning off the LEDs when points are closed/grounded. The complete schematic for my bike is shown below:

    Click image for larger version

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    With the key on and kill switch off, B+ voltage activates a small Bosch-type ignition relay (I originally devised a simpler equivalent circuit using a DPDT lever switch instead of the relay, but couldn’t find a suitable switch with the correct form factor to fit in the handlebar housing). Resisters R1, R2 and R3 are arbitrarily 1.5Kohm/0.5W because that’s what I had around. R1 prevents a direct short when the points are closed. The combined resistors limit the LED current to below 3 ma when the points are open; it turns out this is plenty bright enough to easily be seen. The LEDs are mounted onto a PCB and the board attached to the switch housing. The resisters and diodes are mounted on another PCB located inside a plastic tube and wire-tied to the relay located between the gas tanks.

    When I first ginned this up w/o R3 and the diodes, it worked fine on a breadboard, but the LEDs burned out in 30 min on the bike. After boning up on the high voltage transients/flyback that occurs when magnetic fields suddenly collapse, I added the diodes for LED protection.

    I also shielded the wires to the LED circuit and kill switch, trying to eliminate the effect of any pulse jumping to the LEDs when the kill switch is thrown. As shown below, the wiring at the handlebar is all crammed into one hole so I could envision a HV leak causing problems here. If I’d done a more thorough job I’d have added these different diodes and shielding sequentially to see what the root cause really was, but wanted to finish it and ride. Anyway, after a couple months I can say it’s working and hasn’t failed yet.

    There are two other benefits from this LED setup:

    - I can set the static timing with key on, kill off w/o loading the ignition coil at all. The current draw is 139 ma with the LEDs on, 148 ma off during dwell, most of that’s the relay load. Battery wouldn’t want it left there for hrs on end but it’s nothing during a tune-up.

    - Get bored at a stoplight, I can quickly toggle the kill switch to off, get a short light show, then back up to run w/o it stalling. Simple mind, easily amused.

    The pictures below show the various components during construction and assembly, hope someone finds this useful. The LED(s) could be mounted anywhere you want, of course; the kill switch panel was simply a convenient spot for me. I realize I’m likely reinventing the wheel here, has to have been done by others in the past; this is just how I did it.


    I got to make a couple PCB’s here, muriatic and peroxide:

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    Red LED’s look white to an Android phone:

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    More pix and video on next post.

  • #2
    Drilling the hole in the handlebar took a while, then it’s still a tight fit:

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    Populated board, installed next to the relay between the tanks; there’s reason I kept that old dishwasher hose…

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    Video clips to follow once I load them to youtube.


    • #3
      Having trouble getting videos to load to youtube. Will try again later.

      Up now:

      Real-time video of starter turning them over:

      Slo-mo video showing the short and long flashes:

      Video of kicking it; no guarantees it’ll start the first time, but sometimes you get lucky:

      Last edited by jdmboyd; 05-31-2023, 12:53 PM.


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