gy6 moto coil? anyone tried?

Discussion in '2-Stroke Engines' started by briane, Aug 22, 2013.

  1. briane

    briane New Member

    hey all,

    I'm trying to find a decent coil so I can build my own CDI circuit and play around with timing curves and components.

    Anyone used this gy6 before? would it work on a skyhawk 2012 with an appropriate CDI?

    I've tried the jaguar - prolly just me cause I hear everyone has great results - but my jag CDI lasted about 5 rides before it died - so Im not impressed or going that route anymore - I'm gonna have to build my own I think. Also the jag is built around top speed, not low end torque - and I need that torque to get up hills - so not only the quality issue, but that jag didnt do what I wanted it to. clearly I need to design my own. sorry jag - I really respect your info but it did not work for me.

    and yes - I am an electronics guy who designs his own circuits - I figure if I just get the coil I can build my own electronics. So yes, the jag was installed correctly, and had no broken wires.

    oh - just noticed jnm has a warranty on that jag cdi - maybe I just got a faulty one?

    still want to build my own.

    ps - I've built most of the consumer grade electronics in my home - this is basic stuff once I figure out what needs to be done

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  2. Fabian

    Fabian Well-Known Member

    Can you design and manufacture a CDI and coil that uses a graphical interface to steplessly adjust the ignition timing curve, and most importantly runs a twin spark plug cylinder head.
    I have a burning requirement (sorry the pun) for a CDI/coil that can perform this function.
  3. briane

    briane New Member

    sorry - I probably should have labeled this thread ' what coil can I use to learn to design a CDI around' - I dont mean to come across as a know it all, just tryiing to say I'm not totally out of my boat here - but yes I recognize and value the experience you all have. I thought this would be a fun electronic tuning project for me.

    sorry fabian - that wasnt my intent - I just want a bigger spark and maybe the stock low end timing curve - and some electronics I can muck with. I have since realized that aside from hotter spark the best way for low end torque might be a sproket change. no, I dont want a gui on the thing - though it would be cool - Im fine with resistors and caps.

    thanks sublunacy, I'll look into the mitsubishi coil.
  4. Fabian

    Fabian Well-Known Member

    How much more torque do you need?
  5. briane

    briane New Member

    yeah - truthfully I was going to start with jags ideas - I dont want to re-invent the wheel, I just want it to help me grind up seattles crazy hills. I had though ripping apart a stock cdi - and bypassing the coil to a larger one would be a start - but I also dont want to 'steal' someone elses invention (ie. thanks jag for the schematic - occured to me I'd learn a lot building one and messing with values a little bit)....Though this is all personal use and sharing to me. Im interested in the single/double pickup cdi (is this the 2 stroke/ 4stroke timing difference?) issue so I'll have to read up on that.

    also - regarding the .3 ohm rotor - are you saying say a .5 or 1 ohm would have better spark? Then to me since this could potentially become an experiment in excess - if cost and size were immaterial - whats the best ohmage for these little 2-stroke 66cc chinese engines?

    I recall jags cdi did work really great on the top end of the acceleration.
  6. Fabian

    Fabian Well-Known Member

    How much more torque do you need?
  7. Fabian

    Fabian Well-Known Member

    If you make a new CDI, i'll get out my credit card and buy the thing ASAP, because i'm curious to see how someone else's idea works out in practice.
  8. HeadSmess

    HeadSmess Well-Known Member

    is the jag still built on veroboard and unpotted?


    not saying what components go where :jester:

    the "lighting coil" is heavy guage, wound from the earth tap to the white wire.

    the "charge" coil is finer guage, starts at the white wire tap, and continues on to the blue wire.

    any fluctuations in the load on the lighting coil will affect the timing on the cdi, to the point of not running most of the time.

    dont use the white lighting coil. well, you can but usually its a waste of time.

    the cdi operates by charging capacitor on the positive swing, triggering and discharging at a certain voltage on the negative swing.

    theres plenty of ways to vary that timing... the CR circuit seems to be the way someone posted it in a forum somewhere, and whats been used on the available models. its easy, doesnt require an abundance of parts.

    theres other ways.

    back to the main question. what coils work? so far, on my simple unretarded cdi, ive managed to get anything from a 2.4v mains transformer in reverse, a car coil, the old points type, a new car coil, a pitbike coil, the flyback from an old HF welder starter, the flyback from a telly, a postie bike coil, and even just an old solenoid coil with a few turns of wire round it as a primary!

    and, so far... with four different cdi's and various retard/advance curves... nothings beating the basic 8 component CDI circuit.

    (this isnt it, but close)

    briane likes this.
  9. HeadSmess

    HeadSmess Well-Known Member

    ill also add. its not my circuit. that ones of russian heritage i believe.

    the minor difference between it and what i use is to change the resistors to just 82R and 18R in series, centre "tap" being "wiper" on trimpot shown... 82 goes on the "black wire" side, 18 to the junction of diodes and thyristor cathode. use 1watt.

    thanks to "rohmell".

    it is a pretty standard circuit though. cant give that much credit. found it in flash tube drivers, fence chargers, etc... i even have a novelty lighter that has one inside for zapping the unwary! oh, the time i got the boss after he had just washed his hands :rofl:

    i figured a way to increase the advance drastically by changing one component. i think. i need a scope and to actually assemble such a beasty to verify :) designing PCB's is all good and well, but redesigning circuits and making sure they work is more important!

    youll find starting is much easier as spark energy is increased. a much more effective circuit.

    this one produces sparks powered from 15v tap on a mains transformer, the stock HT just starts at 60! works to check, but dont run too long as the current drain on the negative cycle overloads the resistors. it was a 5 amp transformer though... :jester:

    also, theres talk of using the rest of the negative cycle to use as a 12v power supply. the thyristor uses a poofteenth of the energy produced to trigger.

    im working on this. i didnt like the example shown... same as that white wire coil i talked of...changes trigger voltages, affects timing. needs to be "isolated" somewhat.

    all this adds to the size and complexity of the board.

    for playing around, heres a basic board...


    outputs on left hand side from top are black blue coil.



    feel free to play with the 47R, 560 R, and the 2.2uf... or even remove em ;)
    Last edited: Aug 27, 2013
  10. HeadSmess

    HeadSmess Well-Known Member

    im more interested in ignoring any existing graph, and doing comprehensive dyno tests to get the best graph.

    meanwhile, i have a concrete ring to repair. and an agitator motor. gotta pay for food somehow. grrr.
  11. HeadSmess

    HeadSmess Well-Known Member

    a dyno is used for evaluating what affects any changes make to the performance of an engine. regardless of what those changes are. some people dynotest just to show they make 0.3% more power by using ceramic bearings...

    an ignition curve can have a major impact on performance with or without pipes.

    how an airfuel sensor can have any bearing on determining correct ignition timing, iunno.

    and how exactly would i adjust the fuel map on a steam engine if that was what i happened to be testing on the dyno that day?

    maybe the same way i would tweak the mixture on a 32kv wound brushless motor, seeing as thats been on a dyno to see if the extra gain in power was worth the extra current draw due to rewinding with two less turns...

    all this nonsense about "this retard curve is the ducks guts because i say so and it felt smoother and got up a hill 2km/h faster than yesterday" is BS. i want definitive results, not the propaganda spat out by a salesman or someone trying to prove what they cant.

    but i do agree that an exhaust is a much better upgrade than some ignition circuit!

    basic circuit works well enough for me. just some people are willing to pay for gimmicks if theyre convinced enough...
  12. Fabian

    Fabian Well-Known Member

    The Jaguar CDI works well. If it didn't it wouldn't be on my bike.

    Having said that, i want an upgraded version of the Jaguar CDI that allows me to interface between my laptop and the CDI so i get get inside the thing and have total control over the ignition timing in a stepless arrangement.
    I want to be able to drag my mouse and adjust the ignition curve to wherever i choose it to be.
  13. briane

    briane New Member

    wow thanks for all the great info - I know its not the biggest upgrade - but a hotter coil on the stock CDI would really help - and since that aint likely the best arrangement I thought I would build one myself - ordered a few 2 stroke coils to test out. Once you have the carb and pipe, the electronics seems like one of the biggest weak links, but thats only a guess.

    How long do these stock CDI's last? I seem to only get 25-30 rides before they start acting up - they still work but are clearly weaker. Likely the quality/contruction of this BT151. What kind of rating on the BT151 are people using?

    I'll be building that circuit and try a few tweaks - one thing I think may be missed is the harmonic resonance of the coupling cap - which seems important from reading up - that would a solen peform against a nichicon against sprague against some other brand - one thing I can guarantee is the harmonics on each cap is different.

    yeah - I dont know how scientific this all is - me I have certain runs I do on speed tests with the speedo - but that doesnt say anything except maybe 'goes faster' or not.

    oh fabian - I get you - but thats going to require a digital CDI - which means it needs a computer inside it - so probably have to cut apart a smartphone and put it inside (at least without a dedicated digital circuit, ie cheap re-use) -plus power supply - excessive for my needs - yes highly desirable - but probably not realistic untill smartphones are the size of a fingernail and cost less than 10$ for the really good ones.
  14. Fabian

    Fabian Well-Known Member

    I'm quite happy to pay $600 for an ignition system that does everything i want it to do, i.e. full laptop interface and applicable software, and also a permanent fixture on the bike.

    A narrow band A/F sensor is pretty much useless for the application that is being discussed, because narrow band is only designed for closed loop operation. Full throttle operation falls outside the measuring capability of narrow band sensors. A wideband oxy sensor is the way to go in this situation.
    Some of the German manufacturers use wideband oxy sensors in their vehicles.
  15. briane

    briane New Member

    Actually it is I who am humbled - I have learned a great deal - and now in the process of some reverse engineering on existing products - I'll just leave it at that, but I'm interested in the differences in the circuits using the C106D chip versus the BT151 - same idea, clearly different circuits and design though. I have thought that the electronics are really just providing some timing retardation/advancement - the big stuff is in the thyristor and the coil - so yes maybe I was joking earlier- but I was early saying that a laptop mounted to a front bike rack might be the easyest/cheapest solution for the ultimate 'fabian' solution. The magneto may also be an area of improvements (stronger magnets???, etc...)

    I still want to see more schematics for CDI circuits, using the BT151 - but more improtantly I would like to see some schematics for circuits using the c106D as that seems what some of the higher end guys (ie jag) are doing - I have parts on order, but theres still a bit more engineering I have to just 're-invent the wheel'. I like to build what has been done first, get to really understand it, then go from there as then I can tweak minor part changes and get an idea not just for what does what, but what it influences.

    I dont care if it has 10 or 100 parts in it - I want it to have good spark for starting and climb up those hills like a hunkered down soldier. As far as quantifyiing - for me Im ok with testing and personal biases for now.
  16. HeadSmess

    HeadSmess Well-Known Member

    still havent had a cdi unit fail? had plenty of old magnetos with the white wires burn out, but still, every cdi ive had still works.

    bt151, whatever i got. think they were 600v. never bothered with anything else yet.

    people are getting away with 275volt caps, so...

    the amusing thing about all this "stepless ignition control" is that most engines, even racing engines, seem pretty happy with retarded idle, really quick advance from above idle to around 7000rpm, then start retarding again... whereas the stock HT engine is lucky to do more than 7000rpm.

    but. i have contemplated this harmonic thingy...or maybe you mean reactance? ive been puzzling over how to use the reactance to "filter" the trigger in a way to achieve advance/retard without the CR circuit. iunno. amazing what you can do when being silly...

    possibility of replacing a diode with a 1n5711 or 1n34. lower voltage drop allows trigger voltage and current to flow earlier, achieving advance. shame both components are rated at less than 100v inverse!

    the other thyristor thingy you mention may require a lower trigger voltage/current. hence, more basic advance. other than that, i cant see any need for it. maybe a faster response time? less ON resistance hence more current flow from cap discharging making bigger sparks? iunno who cares :jester: me, maybe...

    the easiest and best method, for all the diehards out there... use the existing magneto as a power supply, rectified and stepped up with a dc switcher etc. then add a hall effect sensor to trigger at 40-50btdc. let the unit work out all the retard required from that point.

    so just buy mps or one of several other overpriced black boxes that really do little unless ones really working at the limit of performance...

    really, i want the dyno just cus its easier than buzzing down the road after every new mod... especially when the mods dont work!

    be nice to actually try timing one of these engines as well lol.
  17. HeadSmess

    HeadSmess Well-Known Member

    just went through the data sheets. c106d is 4A 400v, bt151 is 12A, and cant see any other differences... trigger voltage current is hard to tell... really need the device on a board to test, sheets use different voltages etc on tests...

    farnell says the 151 has a lower trigger voltage which is beneficial...
  18. Fabian

    Fabian Well-Known Member


    The bullsh!t stops when the dyno rocks, plus you have a controlled set of conditions for consistency and repeatability when testing new components/designs against a baseline.
  19. briane

    briane New Member

    yeah - I ask cause the jag CDI uses the c10d6 - I have yet to identify a few of the diodes - but I'm pretty sure their zeners dropping down the trigger voltage - iniaitally looks like 2 .8 volt zeners @ 1 amp - have to check in more detail though - this seems proper as I suspect the trigger voltage on the c106D is a bit less than the input voltage -though I have not had my meter on it yet - so dunno

    So my plan now is to build a multi-CDI unit with switches and a visual plug monitor built in - then I can do a big run (hahha - they just put a city speed tester right next to my house - perfect!)

    then I can just flip the switchses between a few run, and try out 3-4 different CDI's, while also monitoring the visual appearance of the plug spark- not too scientific , but these will be 1/8 mile runs and so should give an idea of relative aceleration. I also have (will have) 2-3 coils I also be putting on switches, which should test about 10 combinations.

    yeah - amp and voltage on the BT151 and c106D are pretty similar - I see the 400 volt in the jag, but sometimes you get better performace out of higher raterd parts - the 600 might be another test..

    No - Im talking about harmonics - a bit of background - I come from the world of building high end amplifiers, guitars, instruments in general - so the harmonics of these brands is one thing I have an (empirical) grasp on. Though whats the effect? - I think it controls the re-actance capabilities - dunno.
  20. Fabian

    Fabian Well-Known Member

    or drag 10 trailers: