12v cdi kit wiring issues

hi, I have recently restored a Peugeot 103 and installed a new crate motor, it came with a 12v cdi kit attached but no wiring diagram, the cdi just plugs in which I am fine with and the other wires are kill switch earth and 3 wires from each of the other coils, I am having some issues, I fully rewired the bike and am getting the following problem.

when approaching 30mph the bike starts to stutter like its cutting out, if I turn the lights off the stuttering stops, if I disconnect the lighting coils totally and only have the cdi coil connected it runs fine, if I hold the coil slightly away from the frame I get sparking like a spark plug in time with the firing from the mounting lug which I have not seen before, the coil is a two wire coil earth and live I have checked and rechecked all connections and swapped connections on the lighting coils as I only need to use one of the lighting coils.

I don't have a regulator installed as I only run 12v bulbs back and front and an a/c horn.

I have swapped out the coil, plug cap and cdi and there is no difference.

its like there is not enough power being generated to produce the spark at higher rpm's and the current draw from the light is starving the coil or there is some kind of feedback.

has anyone any ideas re this and does anyone have a color wiring diagram for the cdi pictured (12v)

I have wired this one exactly the same as my other and its now baffling me

thanks in advance



Re: 12v cdi kit wiring issues

Hey Simon,

Can you make up a diagram of how you have things wired right now?

the only time I have had issues like this are when i did not have good grounding.

Re: 12v cdi kit wiring issues

Are u using the frame as the ground for the 12 v lighting as well as the cdi ?

Re: 12v cdi kit wiring issues

Yes how would i not do that/seperate them as the cdi housing is earthed?

Re: 12v cdi kit wiring issues

I have one of these but didnt use it and i dont have one on my other 103 , i dont get how you would seperate grounds as all switches are metal and front and rear lamps have a frame ground connection


Re: 12v cdi kit wiring issues

Well somehow this is probably the cause. Somehow the two using a common ground is the issue. It runs Perfecto when u disable the lighting circuit. One solution is to float the light coil and create a wired ground returning to the newly floated end of the lighting coil. I don't know if there is a simpler cure perhaps someone like Ryan or Dillon can instruct us.

Re: 12v cdi kit wiring issues

If someone could draw a rough sketch of how that would hapen to a single light on off/ back and front and a horn, cdi, coil and kill switch it would be appreciated

Re: 12v cdi kit wiring issues

Please post your oem 103 wiring diagram. If u do t have it please look on Myron's mopeds and find the exact one and post it here. Need to see how it's already wired. To do what I suggest to my Vespa grande I needed to modify wiring so as to make sure all energy from the light coil found it's way into a.single.wire that I attached to the side of the lighting coil that is grounded at the coil. Please post so if u want to do it , you will see the mods. Your bike is probably 90% there. The issues usually are in the brake circuit. I've never messed with the back side of an ignition coil for a cdi. So alot of the rewire involves the brake light circuits with the brake light switches on the handbrakes. Things often require new switches on the opposite direction with the power flowing when hand brake is squeezed powered by light coil vs the grounding of the backside of the ignition coil as on vespas.

Re: 12v cdi kit wiring issues

that air coil transformer is used in on 5-coil stator bikes to power aux illumination for speedo and running light. i think it pulls high amp 6v flux and transforms it to 12v. and only powers them if the headlight is on.

NOW: you said you have this wired exactly the same as another one? do you still have it? if so - replace known good components until you find your failure point.

i would still like to see how you have everything hooked up, and still will say that everything has to be grounded.

make sure the motor is grounded to whatever you are using as a common ground like the frame or swingarm.

you cant rely on the motor grounding to the frame or swingarm through the motor mounts!

i do not think that sharing grounds is causing your issue.

Re: 12v cdi kit wiring issues

Just to let you know I sorted this issue, my error was -- what i had done was mistakenly taken a branch off from the wire which supplies the coil as the engine cut off instead of the correct pin from the cdi box (the connector didnt even have that wire or female plug installed), that explained the cut out at higher revs as part of the coil spark power was being sapped back into the frame. Also explained the random electric shocks through the handlebars! And hard starting from cold!!! Starts first kick now. Thanks all for your replies, i will punch myself in the face as punishment.

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