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Points to GN250 Electronic Ignition Conversion

Discussion in 'The Garage' started by Jim, Aug 15, 2020.

  1. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Minor update....
    Scrounged the basement stash and found a respectable stator, cleaned it up and installed it along with the modified rotor. I'm a poor man, so I'm using a VR-794 reg/rec that I have on hand as a spare for the SG. Since it's an 'A' type regulator, I modified the brush assembly with nylon screws to isolate the grounded brush.

    Modded rotor.jpg

    Cleaned up stator.jpg

    Added the VR-794 and a Windy Nation rectifier to the panel....

    reg rec.jpg

    .... and we now have an operational charging system. 14V just off idle.

    XS stand Charging 14.0.jpg

    Added a Honda MP08 dual output coil and the GN250 igniter box and wired both up.

    gn box and mp08 coil.jpg

    And considerin' I been know to be absent minded.... :cautious: I modified my switching setup. I put the points and GN power on a SPDT toggle. This way I can't switch to one system and forget to shut the other off.

    toggle sw.jpg

    Wires are ran down to the stator for the trigger, sooo..... it's time to work out the trigger mounting. Stay tuned.
    Last edited: Sep 11, 2020
  2. Smuggy

    Smuggy XS650 Member

    Jim, you are truly a wizard, definitely staying tuned for what's next - amazing work so far, I'm sure this is going to be one of the go-to conversions when you are done :cheers:
  3. Signal

    Signal XS650 Junkie Top Contributor

    While waiting for my GN250 TCI modules to arrive I have mounted a 6mm magnet in the rotor and modified a pickup module so it can mount on the stator.
    I have also marked the stator with a 35-degree advance mark. The systems are intended to be total loss so did not replace the slip ring screws.
    I want full advance to be 35 degrees.

    My questions are:

    · Do I mount the pickup directly over the magnet?

    · Should the rotor be in the 40- or 35-degree advance position.

    Paul Sutton and Jim like this.
  4. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    The box sets the advance based off of idle fire. You'll want the pickup over the magnet at that point... whether that's directly or not is unknown at this point. I'd set it directly over it and leave some wiggle room either side (slotted pickup). While I understand your a total loss system, if the pickup you're using is magnetic, it might sense the screws as triggers. Is the pickup non-magnetic?
  5. itschrisb

    itschrisb XS650 Addict

    Could anyone possibly modify a rotor for me? I don’t have the means to do it but I have a points bike I’d like to convert to GN250 Ignition.
    Jim likes this.
  6. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I could do it for you, but we might be jumping the gun a bit. We haven't made a running example yet.
    MaxPete, gggGary, Team Junk and 3 others like this.
  7. itschrisb

    itschrisb XS650 Addict

    that’s fair. I’ll keep it in mind knowing it’s an option when the time comes!
    Paul Sutton, MaxPete, Smuggy and 2 others like this.
  8. Signal

    Signal XS650 Junkie Top Contributor

    Thanks Jim, Yes I have magnetic pick up. I did think about it false triggering on the screws but thought if the rotor was not energised it would be less of a problem.

    With steel reluctors the pickup must be very close to reluctor to work. I did start to replace the screws but stopped when I had the thought above.

    I will try it and if I have problems I will replace the screws.

    In my mind I already have a 277 degree rephased unit operating perfectly.
  9. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    So I just made a 15min video on testing the RX Z trigger and it didn't record the audio. Sigh... :(
    What I did was check the output of a stock TCI trigger as a baseline and compare that to the RX Z trigger. I re-shot the video (abbreviated) so I'll add that, but here's where we're at....
    ....at 3200rpm the TCI trigger gave us a pulse that peaked at 159mV (millivolts) with a low of -213mV. The RX Z trigger seems to be a bit more sensitive as far as distance, but it looks like the magnet added to the rotor will work. It gives a high of 137mV and a low of -99mV at 3200rpm. I think before I install the trigger and try it, I'll wire up a GN250 box on the bench and see if it will fire a coil at those signal voltages.
    I found a website with good instructions on converting a PC to an oscilloscope but one of the parts has been back-ordered for the last month. It shipped today. So hopefully next week I'll be able to convert my laptop to an o-scope and get a better look at the trigger output.
    Stay tuned.

    MaxPete, Rasputin, Grimly and 5 others like this.
  10. Grimly

    Grimly XS650 Addict

    I'm watching this with interest.
    I have Boyer ignition on the XS, but the GS is chugging along with an ancient Piranha system that's sure to turn its toes up someday, plus it relies on the mechanical advance mechanism, which ain't getting any younger.
    I have a couple of spare sets of factory ignition pickups in good order and I'm thinking they might trigger the GN box, if I install two of these critters.
    What might stand in the way of that would be a disparity in advance curves between the boxes.
    MaxPete, Jim and Rasputin like this.
  11. Rasputin

    Rasputin XS650 Addict XS650.com Supporter Top Contributor

    I have a Piranah system on my 400/4. Been on there, must be 15yrs. Was second hand when I got it.
  12. Rasputin

    Rasputin XS650 Addict XS650.com Supporter Top Contributor

    Jim. It will be interesting to see the wave forms side by side when you get your laptop working as an oscilloscope.
    Greyandridin, MaxPete and Jim like this.
  13. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    The O-scope app I wanted to use is no longer available. I'm still working that out.

    Put the honeydo's on hold to spend some time on this.
    Here's my plan; modify the existing stator so that it will accept a TCI trigger as well as whatever I come up with as an alternative. Can some of you lads look this drawing over and tell me if that's enough info for the average joe to modify it? Thanks.

    Stator Mod..png

    Last edited: Nov 13, 2020
  14. xjwmx

    xjwmx It's just the unknown. Top Contributor

    Jim likes this.
  15. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Looks to have all relevant measurements..........Starting point is the line across the holes.......Basic knowledge on how to use a protractor and the rest speaks for itself.

    a question that has been on my mind...........with the Factory picup it has the 2 coils..........if i am understanding this correctly the idle is based one coil and the advance is based on the distance between the 2 coils = revs
    Jim likes this.
  16. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Thanks Doug.
    Idle is based on one coil, full advance is based on the other. In between the brains (IC chip) builds a gradual transition between the two based on revs.
  17. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    In that case, if an alternative pic-up is used it has to have 2 coils or 2 seperate coil pic-ups spaced the right distance, then they would have to be wired together for the chip to read
  18. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    The TCI requires 2 coils, the GN250 only needs 1. I'm trying to set this up so you can use a single coil from the TCI pickup going to the GN, like my SG is currently set up, or a single, yet to be determined coil.
    650Skull and MaxPete like this.
  19. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Of course.....will be running the GN..............had it backwards in my mind,thinking the Factory TCI on it would need 2 pickups............
    Jim likes this.
  20. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Baby Steps...
    Used my drawing to mark and drill the holes in the stator. Verified correct dimensions.
    Here's a useful tip for running a straight tap; chuck the tap up in the drill press, pull the belt off the motor so the chuck turns free and hand turn the tap down into the hole.


    Stator back on the motor...


    ...and a test fit of a TCI trigger.


    This trigger (pick-up... crank position sensor... whatever. :rolleyes:) is bad. The retard (idle) coil is open. The Baron of Baraboo has a good one wingin' it's way to KC as we speak. I'm going to install that and see if it'll run. We know that a standard TCI bike works. So this will be modeling that with the sole exceptions being the modified stator (shouldn't be a factor) and the pre-TCI rotor that's been modified with the addition of a magnet and brass screws on the ring plate. Once I'm satisfied this configuration works, I'll start playing with different sensors. Like I said... baby steps.
    Last edited: Nov 14, 2020

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