Easy way to add scooter cdi to moped

I modified my hobbit today to run a 2t scooter cdi. (hall sensor added on the case, and a metal strip mounted onto the flywheel to trigger it. Copied the design from a Vento scooter.

Sadly, I realized this particular cdi won't work due to the huge voltage required by it.... 75vac+ :(

Is there a 12v ac or dc low voltage cdi that I could try to swap in?

Preferably with a curve? Anybody know of one?

I could get this to work if I found one....

Thx! (edited)

Re: Low voltage cdi w/curve?


Got spark!

Reverse a wall wart's power that goes from 120vac down to 6-12vac (not dc)

That powers the cdi great! Hook up one side of the former output to a stator line, other line to ground. Then take the former AC plug input, run one to ground, run the other to the cdi AC power.

I ran the trigger across some metal and p0w! Big blue spark.

Might I have just found a way to run a cdi with a curve on a stock points hobbit flywheel? I might just have... Back to work.

Re: Low voltage cdi w/curve?

Running! First pull!

Just have to check real timing, and go for a ride. Then fine tune.

Easiest way to add an AC powered scooter cdi to almost any moped.

Just add a thin metal strip to the outer part of the flywheel (tack weld)

Then add the sensor so it's timed right...then wall wart step up to provide correct AC. Best part is that if the Cdi dies, your points are still ready to go!

Fuck! I'm happy clam!

Re: Low voltage cdi w/curve?

Omg! Runs great. Just took it for a lil ride and it's running cool as a cucumber. Didn't run it for too long, but it's not backfiring or anything. I think Im running really rich with the new cdi now compared to points.

I'm using a stupid conair curling iron adaptor, that is 110v in, 3.6vac out.

Flipped it, and it's giving the output about 75-85vac into the cdi when running. I attached it to the yellow line of the stator, but might try the red line.

Ok, going upstairs to upload pics.

Re: Low voltage cdi w/curve?

Im planning on a few mods to keep it reliable. The strip weighs 4.5g,

so I'm going to weld an identical strip on the opposite side of the flywheel, out of range of the sensor for flywheel balance. I'm also gonna jb weld the sensor to the metal plate, as the large metal plate's bolt holes are slotted so it can be properly spaced. Then of course a lil wire cleanup and securing the adaptor in the lil former carby airbox space.

I thought there wasnt a way to make this work yesterday, but cheap ass wall warts can do you goodly. Garbage recyclers FTMFW!

Re: Low voltage cdi w/curve?

wOW No gay HPI with no lights, Have your cake, and eat it too jbot

Re: Low voltage cdi w/curve?

Yep! I might have just put HPI in some distress if this continues to work. Soory.

This means you can run ANY AC scooter cdi with whatever curve you can find.

Find a junked scooter sensor, buy the cdi and find a wall wart at the garage sale for $1, then wire that beeotch up! POW!

Re: Low voltage cdi w/curve?

Dimensions I did....

Metal strip 1mm thick, 7mm wide X 54mm long. (same as vento)

I placed strip so it's past the trigger 12-13mm at tdc. Managed to set it so the woodruff key is still in place, can adjust timing slightly by sensor adjusting, or by adding a tack or chopping the strip a bit.

Re: Low voltage cdi w/curve?


Re: Low voltage cdi w/curve?

Whoa is right. I'm busting!

Super happy this shit works. Last night I was bummed because I did all the hard stuff, then there wasn't enough AC voltage to run the cdi. Step up transformer dreams..read read, try, do, works, hooray! Proof of concept!

Can't wait to see what experienced moped wrenchers do with this.

Re: Low voltage cdi w/curve?

props to messing around with that stuff but your bike looks like an electrical nightmare!

no offense intended... are you making a wiring diagram to keep track of that rats nest?

Re: Low voltage cdi w/curve?

Its only a nightmare if you dont know what you are doing or understand the concepts. I do. Sounds like you might not.

When I'm prototyping, I'm not worried about looks.

I know the wiring backwards and forwards.

You think this is a rats nest? You should see my robotic band's interfaces. Hundreds and hundreds of wires, but I know what each one does. It's simple.

I'll post some schematics up later once I draw them up. (edited)

Re: Low voltage cdi w/curve?

Captured By Robots is tight, I feel like i've seen your show ... like 6 years ago? Have you been doing it that long?

Re: Low voltage cdi w/curve?

Going on 15 years now...ughhhhhh

Re: Low voltage cdi w/curve?

ok then I definitely saw it longer than 6 years ago. I think it was in Chapel Hill, NC ... anyway sorry to thread jack. really good thing you got goin' on there, i'll be following this thread.

Re: Low voltage cdi w/curve?

I was kinda wondering how you used a wall wart ( Now i have googled the term and figured out what they are ;) ) to step up the voltage ac output.

is it a 12v output? I know they make like a 6v, 9v, and 12v wallwarts.

Re: Low voltage cdi w/curve?

I used a 3.6vac adaptor. Ac to AC, not AC to dc!

It is a simple 120vac transformer.

Wall voltage is 120vac, adaptor steps it down to 3.6vac ideally on this adaptor.

Flip the inputs and outputs now...

Put voltage into the 3.6v output from the stator, the adaptor steps it up to 120vac ideally (but some loss will occur) it would come out of the former wall plug. We need about 75vac to run the cdi.

Schematics tonight or tomorrow.

Re: Low voltage cdi w/curve?

Re: Low voltage cdi w/curve?

There is a switching connector on some cdi's to run a kill switch.

For whatever CDI you get, you can find a diagram of the pinouts or wire colors and what they do using the google.

With whatever adaptor/transformer you wire into your stator line, check the high voltage coming out to be sure it's around 75V ish.... (edited)

Re: Low voltage cdi w/curve?

Jbot, Sure its amazing you can put any cdi on, but what about customizing it?

So i've already figured out a cdi doesn't matter if its 2 or 4 stroke.

So ive been looking for a programmable cdi and there is a possibility there is one out there that will fit the category. Or I guess you just choose one from any scooter and stick with it I suppose.

I found pickups so you don't have to go hacking off scooters


I'm sure they are resold through the internet.




Re: Low voltage cdi w/curve?

why not just run a CDI from a express NU50 and NX50 had a hall effect CDI that would fit

hell didnt later PS50's come with CDI!?!

Re: Low voltage cdi w/curve?

Jbot I have been doing some thing like this and have gone through a few cdi boxes and I have not found 1 that has a good curve they eather have no curve or advance or are cut out over 10,000 what cdi box are you running

Re: Low voltage cdi w/curve?

The point of this is this. In my understanding most modern scooter CDI's have a curve. 4ts do and 2ts do. The 2t cdis are not usable by most mopeds because of the high voltage needed to run them. The only 12vdc 2t scooter cdi i could find was for the kymco agility, but those are restricted.

I'm 99% sure Zumas have a timing curve, this cdi is off a Vento, a china minarelli clone. I have not tested it yet, but I'm pretty sure it has some retarding curve. Even if I'd need to buy a special performance retarding cdi, that still saves a ton of money compared to buying the special flywheel/stator, etc.... And my lights are still gonna rule.

Most older CDI units from the 70s/80s do not have a curve.

That is the point.

I'd rather strip parts off junked scoots (they are a dime a dozen) then buy a $300 setup, and still have points as a backup.

Re: Low voltage cdi w/curve?

I'm following you better after seing the schematic. In the pictures its difficult to make out all your connections. Pow!


Re: Low voltage cdi w/curve?

I had a vento and am pretty sure the timing was static on it

Re: Low voltage cdi w/curve?

I'll find out today. Ill try out my timing light I found at a garage sale.

If there no curve at all, I'll just try a Zuma cdi.

I just cant imagine any modern 2t would run no spark curve at all, especially when even the china 4t CDI's run an advance.

Re: Low voltage cdi w/curve?

Great thread, thanks JBOT

Re: Low voltage cdi w/curve?

I am running that blue one that 77 had for sale no curve I got 2 random ones from ebay same thing I am going to do this on a puch today just to see how it works

Re: Low voltage cdi w/curve?

It retards. Period. Pow!

Went from about 18deg down to about 12deg at 9k.

Fun test, as my bike is screaming and sliding on the floor, but that flywheel is shifting counterclockwise as it revs. Never was able to try a timing light before...cool.

Retards unite!

Re: Low voltage cdi w/curve?


This the one I am running with no curve.it is for a veno but so is about 10000000 other cheap China cdi's.

Can u put up a link to the one you are running

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