CT70 Lighting Coil Exposed

Discussion in 'Tech Area' started by allenp42, Sep 4, 2018.

  1. allenp42

    allenp42 Well-Known Member

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    Damn, you have a good eye. Tightening up the lower stator screw along with loosing the top coil and pulling down to get every bit of the slop out has taken 99%, if not 100%, has cured it. Will check again tomorrow with fresh eyes. I was able to confirm that I have enough clearance without removing timing mechanism...at least on this mitsu. Assuming fresh eyes confirms it, will put it through the paces tomorrow.

    Impressive set of eyes you you have!
     
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  2. racerx

    racerx Administrator
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    Pat has the sharpest vision of the entire board...at times, it's enough to make an eagle jealous.;)

    You are right, as I recall the Mits advance mechanism is riveted to the flywheel. If your CDI module has an advance map, the flyweights have to be fixed in place. IDK...maybe replace the springs with wire, or wire-bind the spring coils...

    BTW...beautiful job winding that coil.(y)(y)
     
  3. allenp42

    allenp42 Well-Known Member

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    I confirmed that a combo of the plate not being tight as Pat pointed out and taking all the slop out of the top coil took care of the problem. The timing advance mechanism can remain intact. Woo hoo.

    However, not out of the woods just yet. I have not installed on the bike yet, but I have checked it out. Got a nice spark, timing advance seems to work, slight difference in amount of advance at lower RPM's (Xtraspares is more) as compared to the marks I made for a Hitachi, but that's about it. It may be my timing light, but I seem to be loosing sync now and then? Would not bet the farm at this point because I've only used the timing light twice.

    The lighting coil has issues. If wired color to color per the directions, HL voltage runs about 9 volts under load and there is not enough charging voltage to generate any charging current even at 8,000. Even with the HL off, I don't see much of anything until 5k and it maxes out 0.6a charging current at 8,000 rpm. This will not work.

    When I swap green and yellow, which is also mentioned in the instructions, charging is ok but HL voltage runs 3 to 4 volts in the range 6,000 - 8,000. Much much lower than anything I've seen before. This won't work either.

    Honestly, not too surprised because I measured the coil resistance before I tested. It has the least amount turns on the charging circuit of anything I've seen that was for use in the US.

    I've sent the guy the details so we'll see how he responds.
     
  4. racerx

    racerx Administrator
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    My bad...I thought you wound this coil.
     
  5. allenp42

    allenp42 Well-Known Member

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    No problem. I wish I could wind a coil that looked that nice. Here's the one I wound and then removed a few turns (reference 149 above).

    But on the other hand, the one I wound works;)

    At this time, not going to make any changes to the kit I received and reduce my chances of getting a replacement or refund to zero.
     

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  6. racerx

    racerx Administrator
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    That's still very clean work. And, best of all it actually works.;)
     
  7. OLD CT

    OLD CT Well-Known Member

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    Here is mine. It's under charging? I haven't tried it on my 4 speed Hitachi yet. It works real good on a 3 speed crank Hitachi with no advance weights.
    Very bright lights even at idle and it doesn't blow HL bulbs or cook the battery.
     
    #167 OLD CT, Nov 6, 2019
    Last edited: Nov 6, 2019
  8. allenp42

    allenp42 Well-Known Member

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    Now that is nice! What I see in your video is what I was hoping to see on the Mitsu setup......by now.

    I have double checked everything, and I am confident the lighting coil is wound wrong or is for another bike. I don't have your eagle eye, but the wire gauge is larger on the xrarespares Mitsu kit I have. Without a doubt, the turns ratio is off between the green & yellow windings. In other words, not enough voltage & current available on the green winding to bring the yellow voltage down. No way for the battery to to be "regulator" and balance out the circuit. It might work on a 3 volt battery but not a chance on a 6 volt.

    What's a little unusual, I have a mitsu stator with a lighting coil that measures very close (scary close) to what I measured on the kit I have, It too has the same short comings. So there is bike somewhere in the wild that uses this type of lighting coil.

    Again, not going to make any changes until I get the green light from the seller, but I'm pretty sure the mounting dimensions for the coil is the same as an OEM Mitsu. I can always pop in a Mitsu lighting coil and then take a ride around the block.

    Once I get over the Mitsu hurdle, Hitachi is next on my bucket list. Personally, I suspect the timing advance curve had to be incorrect on the Hitachi H setups where people reported the kit did not work. The Hitachi coils are the same between a 3 speed and 4 speed and the mounting pads are the same height. It's the pad for the points that differs between the 2. See posts 13 & 14. My point is, if the 3 speed CDI kits works well, I see no reason why the H kit does not work equally as well...or better if the timing advance is correct.
     
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  9. allenp42

    allenp42 Well-Known Member

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    The seller said he tests the lighting coil with a 25 watt 12v bulb. He did not mention testing battery charging. I'm sure the lighting circuit works works with a 25w/12v bulb works, but that pretty much confirms the mitsu kit is not plug and play on a CT70. He is going to try to source a coil that is correct for a CT70. Honestly, not sure if he makes these or if they are a replacement for an older model used in Malaysia? In the last few months, several different sellers in Malaysia are offering what appears to be the same kit? This dilemma would have been super frustrating to resolve if actually installed on a bike.

    Also, I did run across a schematic for an older C70 (I think) that does not use a battery. The yellow wire supplies power for the HL & TL and the green wire just for small lamps. That may explain where the coil for that odd Mitsu stator I have is used.

    A standard OEM Mitsu lighting coil appears to fit just fine. This will work, but I was really hoping for a brighter HL like I see on OLD CT's video (Hitachi setup).

    The seller is being very accommodating and is willing to issue a partial refund. I'll probably give him a few days to see what he finds out on a "better coil" before I take this offer.
     
  10. racerx

    racerx Administrator
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    Weird thought for today...
    You know, as long as the CDI portion works reliably and the seller will be accommodating with the price, this may still be relatively painless way to convert to CDI. A lot of aftermarket conversions fall short of "plug & play". But, it's the ignition that's the most important...especially when it allows retention of the OEM 6V flywheel cover. Outwardly stock appearing can work even for the purists. From what we've seen...largely thanks to your efforts...there are some nice improvements to be had with the lighting/charging system. No reason why a full-wave 12vdc setup couldn't be 6v flavor, as long as a 6v regulator can be sourced. And, if a stock 6v lighting coil will fit the stator, the original 6v/half-wave "balanced" electrical system can be retained.
     
  11. kirrbby

    kirrbby Well-Known Member

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    Well I had LOTS of time to think about a winding jig...maybe too much. My initial, simple plan mostly went out the window. The new plan is pretty involved, but I think it'll be worth it...one and...hopefully done.
    I've been getting a little time here and there, and have a pretty good start on the jig(s). Maybe next week I could have something ready to send you. The wire spool you sent me has a 1" diameter hole thru the center. Is that pretty standard??
     
  12. allenp42

    allenp42 Well-Known Member

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    It spool ID has been the same on all the spools I've ordered. Doubt it will change unless I order a lot, which is very unlikely at this stage. No rush on the winder, but it does have my curiosity up. I'm sure it will be unique.

    If you or anyone else has a trashed Mitsubishi stator coil, I could use one. I may test the water on winding a Mitsu coil. There is one thing I need to learn about the characteristics of mits....where one end is grounded and the yellow is a true center tap. Pretty sure I know but the proof is in the pudding. Again, trashed is better for me. I struggle to scrap a part that can be repaired :(

    Depending on what the warden wants me to do today, I may get around to a quick test of the CDI kit with a used Mits lighting coil...on the bike.

    Once I get my feet wet and get comfortable with the CDI kit, I may dig a little deeper. For sure, it opens the door for a clean and neat conversion to CDI.
     
  13. kirrbby

    kirrbby Well-Known Member

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  14. allenp42

    allenp42 Well-Known Member

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    One similar to that will be just fine. Do you by chance know the dimensions of core? I'm guessing somewhere in the range of 13mm x 8mm.
     
  15. kirrbby

    kirrbby Well-Known Member

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    You're probably right on the core size. I had it at ¼x½" roughly.

    But #8 in that thread was to show you where they grounded the wire, at the start of the coil.
    They soldered it on, then ran it straight down the core to the opposite end, covered it with the plastic wrap, then started winding the coil from the tail end of the steel core.

    I can get a better, metric, measurement of that rusty old Mitsubishi coil tomorrow at work.
    But I'm sure I can find you a better crappy Mitsubishi coil. That rusty one...is rusty! Probably not the best for scientific testing :geek:
     
  16. racerx

    racerx Administrator
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    You've piqued my curiosity. Do you think it's possible to increase output by removing some metal from the armature to allow more turns of wire?
     
  17. allenp42

    allenp42 Well-Known Member

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    Not 100% sure, but I have seen pretty much the same results from a stator rebuild kit that has 1 less lamentation than an OEM Honda. That surprised me, so much so that I'm going check it again. If I see the same, it tells me that someone did their homework and probably have it modeled. Lamination material and material Quality is another area where I'm lacking knowledge.

    The main reason I need the dimensions is to determine how many turns I can get with different gauges of wire. May save me a few steps, I have an EXCEL spreadsheet where I plug in the dimensions of the core, diameter of the wire and get close on the max number of turns I can get and it still fit on the plate.
     
  18. allenp42

    allenp42 Well-Known Member

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    Oh yeah. I've read your posting a couple of times. The mitsu coil and Hitachi coils (77 - 79) share the same trait. One end of the coil is grounded, the other end is Green and Yellow is a tap. K0 - 76 the "center tap" is grounded but the windings are asymmetrical. In other words, the tap is not in the center of the winding.
     
  19. kirrbby

    kirrbby Well-Known Member

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    That Mitsu coil is VERY close to ¼x½"
    .253x.52" maybe...using my super accurate plastic caliper.
    15733287078168872849052370034823.jpg
     
  20. racerx

    racerx Administrator
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    This is the crux of the entire issue, imho. They did intend the system to bias the output toward the HL circuit. (Which begs the question: "what would happen if the yellow & white leads were swapped at the wire harness-to-stator plug?"...I expect that would only "free up" 2-5W max.) From an OEM perspective, it made sense...cheap and effective...for a while.

    Obsolete tech considerations aside, the laws of physics have a lo-o-ng shelf life. If there were a way to lift the coil ground, there's probably enough copper windings to deliver an acceptable amount of current to a full-wave reg/rec unit, which segues neatly into my ridiculous-idea-of-the-day. Is it possible to partially unwind the coil, splice & insulate to create one continuous winding and would anyone be motivated enough to try?o_O
     

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