Magneto Power

Discussion in '2-Stroke Engines' started by Fabian, May 19, 2010.

  1. Fabian

    Fabian Well-Known Member

    Call me an idiot for asking this question, but does the standard Happy Time style magneto have enough power to run "two" CDI's and naturally "two" sparkplugs?


  2. Al.Fisherman

    Al.Fisherman Active Member

    I doubt it, barely has enough for a light. Hook up a secondaty CDI and hang a plug and report back here.
  3. Flapdoodle

    Flapdoodle Member

    Interesting thought. My approach would be to unwind both the white and blue winding, counting the number of turns on the blue one. Purchase enough magnet wire of the same size as the blue, and make two CDI windings.

    Then there would be the problem of drilling and tapping for a second sparkplug... Likely a job for a machine shop.
  4. 210061741

    210061741 Guest

    Why would you want to add a 2nd plug to 1 cylinder.

    I don't think it would gain anything.
  5. Fabian

    Fabian Well-Known Member


    You must be psychic as you're obviously reading my mind.
    The notion of running CDI and sparkplug redundancy has always been on my mind, not to mention more consistant combustion, just like the Rotax 2-stroke 582 aero engines.

    A side benefit, is to be able to run two sparkplugs with slightly different heat ranges.
    This would be quite handy with the jetting i'm currently running.

    Last edited: May 19, 2010
  6. Fabian

    Fabian Well-Known Member

    So, how much energy is required to run two sparkplugs and CDI's and how much energy is the standard magneto capable of producing?

  7. Flapdoodle

    Flapdoodle Member

    That would do as long as one plug was not so hot as to cause detonation, but then the compression ratio on an HT may be so low that detonation isn't possible.

    An experiment could be done... Try a second CDI wired to the original coil with a sparkplug dangling from it. There is a slight chance that the original coil could handle two CDI.
  8. 210061741

    210061741 Guest

    The original coil barly handles 1 plug.

    I think it wouldnt do anything.

    It would have too low of a charge.
  9. Flapdoodle

    Flapdoodle Member

    After a brisk 2 mile ride to warm the engine, I connected a second CDI.
    The idle slowly dropped a little I guess because of the added load, but then it settled nicely. The idle was as smooth as it has always been. Disconnecting the second CDI made the idle speed up again to where it was.

    Why do you say it "barly" handles 1 plug?
  10. wildemere

    wildemere Member

    The early Yamaha DT250 had a 2nd "backup" plug. In those days plug fouling was common.

    These with days modern plugs and oils its not required.

    Even if you could get 2 CDI's running in parallel of one or even two coils I doubt the timing would be the same given the quality of these parts.

    Two plugs in series might work,with really small gaps though.

    Twin spark engines work well when there is a large bore for the 2 flame fronts generated.

    In a bore less than 100mm one spark is enough i think.
  11. 210061741

    210061741 Guest

    I only say because i have burned out a ton of coils.

    Every time i turn around there cooked.

    I'm more interested in using a real cdi.
    And a real coil.

    Like this.

    That would do something for you.

    And yup it's programmable and it'll run lights.

    But even a cheap setup would allow you to tinker with the timing , run lights, and dramatically improve the engine performance.

    Oh yea if you use a good racing crank it'll help too.
    And make setting up that ignition a snap.

    Here ya go.

    Easy mods ...not really but the payoff in performance would be well worth it.
  12. Flapdoodle

    Flapdoodle Member

    Those are some very impressive accessories. Seems to me like it would be like putting a turbocharger and power windows on a Yugo though.

    But back to the topic of the thread... I found M14 x 1.5 taps (not just thread chasers) on eBay for about $8 USD that could be used to make the second sparkplug hole.

    I have wound coils with Chinese made magnet wire and was horrified when I saw the places that did not have any enamel. No wonder many of the magneto coils fail. A rewound coil using good quality wire should last well in spite of the vibration and temperatures it has to endure.

    Once wound, it should be varnished. Overall cost would be quite small.

    On the subject of timing, I advanced mine by 5 degrees simply by filing the woodruff key. Time to do it, about 20 minutes, cost zero.

    I would not expect blazing performance from a dual ignition Happy Time, but it would do wonders for peace of mind having the redundancy on a long road trip.
  13. Fabian

    Fabian Well-Known Member

    That's exactly my motivation for running a dual CDI setup (in parallel) and dual sparkplugs: redundancy on a long trip, as some of my trips are in excess of 60 miles, return journeys.


    Did you have an operating sparkplug attached to the CDI plug wire when doing your test, and how bright did the spark appear to be.
    Once under a high pressure situation, like a combustion chamber on the compression stroke, it's much more difficult to get the spark to jump a gap, that it would normally do at atmospheric pressure.

  14. Fabian

    Fabian Well-Known Member

    Hi Rich

    Although i'm waiting for your parts to begin a production run, i would be most willing to purchase a complete reproduction engine with all the parts you've listed in your post.

    I'm especially fond of the programmable CDI, and any other electronic components that have adjustable parameters.

  15. Flapdoodle

    Flapdoodle Member

    You are exactly right. I did not have second plug attached for the reason you mentioned (no way to test it under pressure), and *if* I were to made a dual, the second CDI would be on its own coil.

    My reasoning was to see if it would handle the load of a second CDI in this test. Not a perfect test, but I am reasonable sure it will work.

    Electronically speaking, the load is the same if the two CDIs are on the same coil or a second coil on the same core. That's why shorting the white wire to ground can kill the engine.
  16. Fabian

    Fabian Well-Known Member

    I am not totally up to speed with the electronics of CDI's, but if you didn't have a sparkplug attached to the second CDI, there would be no current drain from the second CDI.

    Do i need thought correction on my assumptions?

  17. AussieSteve

    AussieSteve Active Member

    I think that you're right, Fabian. Once the capacitor in the second CDI is charged, very little current would be consumed if it wasn't being discharged and re-charged regularly.
    On an aside, it's not generally recommended to power up a CDI unit without a plug connected - it can cause the unit to fail.
  18. wildemere

    wildemere Member

    Why not just carry a spare coil and CDI in your toolkit?
  19. Fabian

    Fabian Well-Known Member

    Completely logical answer Wildemere, but it's certainly more convenient to have both CDI's installed on the bike, not to mention a more consistant idle (if both the CDI's are receiving usable power) and a more unique look.

  20. 210061741

    210061741 Guest

    The Exhaust you use and the carb u use will make a huge difference in the idle.
    If the engine dont have to work to breathe it runs much smoother.

    The other setback i see is there isn't enough material in the stock head to drill and tap a correct sparkplug hole and by the way the sparkplug seat has to be correct or it will leak and the heat transfer from the plug to the head will not be right.

    I am interested in the rewinding of the coil.
    If you can post some pics and a how to that would be great.
    I have 4 coils that are bad that i would have no hesitation in trying this out.

    Also i believe if you use the right gage of wire and a different number of wraps you can actually increase the amount of voltage output.

    Rewind coils yes yes yes.

    Run 2 plug IDK.