AC-CDI v2.7

ACCDI v2.7 up to 350cc

ACCDI v2.7+ for above 350cc

What is better on ACCDI v27 ?

Easier No jumper to cut or to sold. Every function has its own DIP Switch.
Universal More DIP Switches to adapt to different engines.
Safe 2 types of input to stop the ignition: Ground to Kill and Power to kill.
Powerful V27: For 50 to 350cc engine with a 1uf 200volts capacitor.
V27+: 50% more energy for bigger engine from 350 to 800cc with a 1.5uf 400volts capacitor.
Reliable V27+: High quality trimmer. (European Piher brand)

How does it works?

On an ACCDI based engine, the charging coil (AKA stator) puts out:
– LV (Low Voltage around 12Vac) for light and battery if any. (Lighting coil)
– HV (High Voltage around 100Vac) to charge the ACCDI. (Charging coil)
This AC-CDI only uses the HV coil to charge a capacitor through a rectifier bridge.

When the pickup is triggered, the CDI turns on a thyristor that discharge the capacitor inside the primary of the ignition coil.
This burst of energy into the primary induce a high voltage of few thousand volts into the secondary wiring of the ignition coil, enough voltage to create a spark at the sparkplug contacts.


– This CDI works with 1 pickup and 1 reluctor (the metal strip on the flywheel) [A,B].
– This CDI works with 2 pickup and 2 bars [E,F].
– This CDI DOES NOT work with 1 pickup and multi-pulses pickup (ie 2 reluctors on flywheel) [C,D].
– This CDI DOES NOT work with 1 pickup and missing tooth flywheel [G].

– When the engine has only ONE pickup, the 2 wires are connected to HI and GND inputs.
– When the engine has TWO pickups (for Low speed and High speed), the 3 wires are connected to HI, LO and GND inputs.

Pickup Polarity

Be careful: If the wires are swapped then the pickup polarity will CHANGE !

A genuine Yamaha pickup is often Positive first then Negative (PN) but if you swap the 2 wires of the pickup, the polarity will be Negative then Positive (NP) therefore the DIP switches setting for PN will NOT work anymore of course !
Solution: Rectify the pickup connection or use the settings for NP engines.

To find the polarity connect the pickup to an “old” Analogue meter set to it’s lowest voltage setting (around 1volt).
When a non-magnetized steel object (eg a screwdriver) is approached and comes into contact with the top of the magnet the meter needle will indicate a momentary deflection (ie – negative or + positive volts).
When the screwdriver is removed from the magnet’s top the meter needle will show a brief deflection in the opposite voltage. See: Video


List of bikes with 1 pickup this CDI works on.
List of bikes with 2 pickups this CDI works on.



SW13 setting

SW13 switches.


You have to know if the bike has 1 or 2 pickups.
And for each pickup what is the polarity: PN (Positive then Negative) or NP (Negative then Positive).

Connect a scope between Ground and pickup wire to check the polarity.
If you don’t have a scope at hand, you can see the polarity with an old voltmeter.
(See video ).

If you still don’t know you will have to test every possibilities… Follow those guides:
ACCDIv26: Tests all settings for 1 pickup.         ACCDIv26: Tests all settings for 2 pickups.

ACCDIv27: Tests all settings for 1 pickup.         ACCDIv27: Tests all settings for 2 pickups.

SW14 setting


SW14-1, SW14-2: Advance timing
4 strokes engines: set Switches N°1 and 2 of SW14 to OFF (default).

On 2 strokes engines it’s necessary to lower the timing at HIGH RPM:
2 strokes with Small reduction of timing : set Switch N°1 of SW14 to ON.
2 strokes with Medium reduction of timing : set Switch N°2 of SW14 to ON.
2 strokes with Large reduction of timing : set Switches N°1 and 2 of SW14 to ON.


SW14-3, SW14-4 : KTM setting
All engines, set Switches N°3 and 4 of SW14 to ON (default).
KTM engine, set Switches N°3 and 4 of SW14 to OFF.


SW14-5: pickup Sensitivity
Pickup that puts out 2 to 30volts, set Switch N°5 of SW14 to ON (default).
Pickup that puts out 30 to 150volts, set Switch N°5 of SW14 to OFF.

SW14-6: Not used
Can be on or off.



A Kill switch input is available “K“.
Ignition stop if connected to GROUND.


A Safety switch input “S” is available (for Side stand, Clutch, Neutral, Main switches…)
Ignition stop if connected to +2v to +12Vdc.


– If the charging coil IS internally grounded, then connect the only wire to “ALT” input and leave “ALTg” not connected. Note that DIP SW13-6 will have no effect.
– If the charging coil IS NOT internally grounded, then connect the 2 wires to “ALT” and “ALTg” inputs; Order has no importance.

SW13-6 DIP ON: Less voltage.
SW13-6 DIP OFF: More voltage (default).


LEDs have “N” and “P” labels.
They turn on when the CDI receive a Negative or Positive pulse on HI input.


A tacho output “TAC” is available. The output voltage is +12v (even if no battery or 6v battery)
Notice that it’s not a pure square signal.
Connect a tachometer that does NOT need a 50% square signal (50% off, 50% on)


  • How To wire this CDI?
  • How To hook this CDI on a Yamaha XT600
  • How To hook this CDI on a Yamaha XT550
  • How To hook this CDI on a Suzuki GN/DR400
  • How To wire this CDI to a 2 cyl 2 strokes?

  • BOX

    This ACCDI fits in this IP54 box.
    IP54 rating means protected against sold objects and dust but is not fully dust tight (5 out of 6).
    and protected against water splashing from any angle but not waterproof (4 out of 6)
    To make it waterproof, once you are done for ever with settings, pour the box with PU resin or silicon sealant.
    Fill up wiring hole with hot glue.


    Click here for more info

    You will need a DC voltmeter. The best is an old “Analog Needle meter”.

    Step 1

    Download troubleshoot step1
    – Don’t connect any pickup.
    – Don’t connect the Kill Switch or any Safety switch.
    – Connect the GND plug of the CDI to the ground (minus battery or motorcycle frame)
    – Connect the ignition coil to the COIL output of the CDI.
    – Remove the sparkplug from the engine and connect the metal body to a GOOD metal frame (an unpainted bolt).
    – Connect a DC voltmeter between GND(ground) and KILL pad.
    – If the stator/charging coil IS NOT internally connected to ground, it has 2 wires:
        – Connect any of them to ALT and the other to ALTg input of the CDI.
        – DIP Switch SW13-6 can be ON for full rectification or OFF for half rectification (Don’t hesitate to test both position).

    – If the stator (charging coil) IS internally connected to ground, (One wire is already internally connected to ground):
        – Connect the only output wire of the charging coil to ALT input of the CDI.
        – DIP Switch SW13-6 has no effect. (can be on or off).

    Other DIP switches positions don’t matter for step 1.
    – Kick start or electric start a few times to load the capacitor.
    The voltmeter should raise up to 100 or 200Vdc then quickly decrease.
    (Due to the capacitor discharging into the CDI and the voltmeter).
    If not: Check grounds, connections, joints, charging coil (stator), change switch 6 position.

    Step 2

    Download troubleshoot step2
    – Same connections as Step 1 (Still no pickup, no kill nor Safety switches)
    – Turn SW13 DIP Switches positions 1, 3, 5 to ON.
    – Turn RV1 to the minimum resistance (Position: 0).
    – Kick start or electric start a few times to load the capacitor.
    – Once the main big capacitor C1 is charged and the voltmeter shows 100 to 200Vdc, then in the same second:
    – Connect the + 12v battery to HI input:
    – Labeled “P” Led turns on.
    – The big Capacitor discharge into the ignition coil and one spark must fire at the sparkplug.
    If not: Check grounds, connections, joints, SCR, ignition coil, spark plug cables, spark plug.

    Redo this Step 2 but this time connect the +12v battery to the LO input. (Led won’t light.)

    Step 3

    Download troubleshoot step3
    – Same connections as Step 1 ( Still no pickup, no kill nor Safety switches)
    – Turn SW13 DIP Switches positions 2, 3, 4, 5 to ON.
    – Turn RV1 to the minimum resistance (Position: 0).
    – Connect the pickup coil between a GOOD metal frame (ground) and HI input of the CDI.
    – Kick start or electric start to load the capacitor and send trigger pulses:
    – The main capacitor C1 is charged and the voltmeter should read 100 to 200Vdc.
    – At the same time, when the piston approaches the TDC and passes in front of the pickup, a pulse is produce by the pickup:
    LED blinks. (P or N or both leds according to the type of pickup)
    – The pickup pulse then trigger the SCR and the big capacitor C1 discharges into the ignition coil, a
    spark must fire at the sparkplug.
    If not: Check grounds, connections, joints, pickup coil, RV1 is set at 0, reverse the 2 wires of the pickup coil.


    Suzuki GN400 with ACCDIv27+

    Click here for more

    Pickup polarity (PN or NP):

  • Marty bought a 1984 wrecked XT600 without ignition and harness wiring.
    Got it running again even if it seems like he has some carbs works to do…
  • Analog CDI v2.4 on a XT125/1982:
  • Analog CDI v2.4 on a XT400:
  • Analog CDI v2.4 at 15,000rpm:

  • 3 Analog CDI v2.6 on a outboard Suzuki DT30C (3cyl 2stk)
  • 24 thoughts on “AC-CDI v2.7”

    1. Hi
      Does this CDI support 1990 Honda cr250

      Mine has been stolen and I couldn’t find any alternatives that fit
      And the only available cdi boxs for this model are in Ebay and they are extremely expensive even though they are in a nasty condition

      If this model fits my dirt bike I will buy it

      1. Hi,
        I don’t have any direct feedbacks on Honda CR250. Nevertheless looking at some info I gathered on www, It should be OK:
        Honda CR250 – 1900 is a KZ3 model
        – Only one external pickup.
        – Only one metal tab on the flywheel that seems to triggers at 10° btdc
        – A charging coil into the stator.
        – A CDI Box for CR250R (1989-1996) OEM 30410-KZ3-004
        Parts list:–CARTER-MOTEUR-GAUCHE–BOITIER-CDI/13KZ3L41/E__0600/1/4291
        I didn’t find a wiring diagram of the bike. Do you have one?

        You will also have to check if the pickup is still Negative then Positive (like Honda’s)
        A simple oscilloscope trace will tell. An Android phone + 2 resistors can make a scope.

        As a 2 stroke engine, you’ll have to set SW14-1 and SW14-2 (

        1. Добрый день!
          Подойдет ли Ваша схема к мотору Hirth f33 ? Там CDI использует 3 провода,
          1) вход с высоковольтной катушки генератора
          2) масса
          3 ) выход на катушку зажигания

      2. Me too but how do you find out if it will work on a 2 cylinder cm400a hondamatic 4 stroke motorcycle that’s the one I need ..

    2. Hi
      Thank you for your reply

      Yes it still NP pickup coil

      I have pictures of the oscilloscope and I have the wiring diagram
      How can I send them to you

      Thank you so much

          1. There is about 3-4 hundred of us 1979-1982 cm400a hondamatic 1984 450 handamatic that all need a replacement cdi box they are rare and it would be great if you built one for us that would work we could use our own wires from the old one and just solder them onto your same board it would be a real good thing .

    3. Please help us.. we have all the wires and connectors from our old dead CDI modules Nippondenso Part Number 070000-0550 I would buy 2 of them like everybody else that has the same problem and the same bikes mine is the 1979 CM400A hondamatic it’s a great bike just no spark and I really want to put a new CDI made by you people into my bike

    4. The 1979 nippondenso 070000-0550 cdi has 11 wires on it all color coded it’s a small cdi board but they sealed it into epoxy about 4 decades ago and it’s real hard to get apart I was able to get mine apart without breaking the circuit board but the component side is still encased in epoxy and it is just almost impossible to get it off I tried everything . But you seem to make a way better CDI so I would rather get a brand new aftermarket CDI from your company like the other people in the group All I want for Christmass is for somebody to build this CDI

    5. Wow that CDI you build is a beautiful looking thing i have been searching everywhere for people like you that actually can build such a Beauty of a thing ..I just thought I would mention that to you . I bet you it wouldn’t be that hard for somebody like you guys to just make a couple additional changes to this CDI you built and it could probably be made to work just fine .. I am just saying . Anyways merry Christmass and all that jazz keep on biking and keep up the good work …

      1. Hello,
        Thanks for your kind words. Are you sure it’s the CDI? you’ve crossed everything else? kill sw, sparkplug, cap, charging coil, pickup… Well it’s a 40years old electronic, no surprise it’s dead!
        From what I saw on Youtube there is only one magnet on the rotor and only one pickup. Since Honda CM400,CB400 are 360° crankshaft engine, I’m sure it’s a wasted spark system, that mean only one ACCDI v27 could be used. (Or ACCDI v10 is you want better performance)
        I don’t have the bike at hand obviously, so you’ll have to do some test to find which wire is which.
        Follow up on PM if needed. Contact on top and bottom of the page

    6. Hi,

      Have a 98 Skidoo Mach 1 with rotax 3 cylinder 2 stroke. This has an immobilizer and is a one year only cdi. No longer available. Its a pretty high output 134hp 10k rpm 2 stroke.

      The 120 degree seperation 3 cylinder fires wasted spark on all three cylinders everytime one of the 3 triggers are passed by the pickup coil.

      Your instructions say your boxes will not work with one pickup and multiple coils but I think 3 of your cdi’s would work fine in this engine, yes?

      If so since I have to buy 3, which woukd you recommend or perhaps its best to modify yours on a new circuit?

      1. Hi,
        As per your description, yes 3 cdi would work. (This Suzuki 3cyl outboard runs on 3CDI)
        The pickup coil will trigger all of them at the same time (wasted spark) and charging coil will charge all 3.
        BTW if this is the same wiring as yours, there are 2 charging coils, that must be figured out (why and how to wire them?)
        Also you’ll have to know what the pickup polarity is. (PN or NP) Even though wires can be swapped…
        If you consider ordering, contact me prior to order

    7. Bonjour,

      Bravo pour votre site et votre travail sur les CDI qui permet de sauver certaines machines !

      Dans le cas d’une moto avec un seul capteur comme mon Yam DTMX125, y a-t-il un avantage à utiliser la version 2.7 par rapport aux versions plus anciennes ?
      Et est-ce que le potentiomètre a une utilité dans ce cas puisqu’il n’y a pas de saut à régler entre deux capteurs ?


    8. Bonjour,
      La question ne se pose plus vu qu’il n’y a plus d’anciens modeles.
      >puisqu’il n’y a pas de saut à régler entre deux capteurs ?
      Non. le potentiomètre gére le saut entre les 2 impulsions du même capteur lorsque “l’aimant” du stator arrive puis quitte le pickup.

      1. Merci pour votre réponse.

        Si je comprends bien, dans le cas d’un seul capteur, l’impulsion négative est aussi utilisée après redressement ?

    9. Hi Thierri,
      I have my ACCDI v2.7+ and have been working-out how to wire it for my SRX600. I think I understand now but there looks like an error on your XT600 wiring diagram – the charging coil wires (Red and Brown) are shown going to the ACCDI ALT and GND connections when you text suggests it is ALT and ALTg (?) – that had me confused!
      Anyway, I hope I understand correctly and look forward to getting it working. Thanks for all your good work.

      1. Hi Tim,
        Reload the wiring diagram, I’ve changed it. On recent ACCDI2.7 it’s now ALT and ALTg.
        (ALTg can be connected either to gnd or to full rectification with SW13-6)

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