Problems getting a spark, CDI fried? Help!

Thanks for all the help guys.

Yes, I am using a multi-meter to check the ohms, sorry, that is what I ment.

The magneto checks out just fine, reading a little high on the multi-meter (like 410-440) but the magnet rotates, I know it isn't on backwards which is something I read happened to someone... it's pretty much a brand new magneto, not even the slightest hint of discoloration.

Just updating, I'm about to order a new CDI, I have tried every freakin test with this thing and resulted in nothing. I'm hoping it was just my luck and I got 2 bad CDI units, but I might order another magneto just to play it safe in the future... Best vendors for these electrical components anyone?

Still looking for the root of the problem. My dad just thinks I'm unlucky haha.

EDIT: Magneto Mystery is a good read, will try some of these tests while I wait for a new CDI.
 
a while ago we got some stators in that were reading around 450ohms

the really old ones used to read around 250ohms & made bikes a bit hard to start so they started making them around 350ohms (more windings) - when we got the 450s in, we were worried about frying CDI units, so sent them back

not sure if these extra windings will cook a CDI, but we didn't want to try it

dig your meter probes in really well to get a clean connection, and if it is still reading high, you might want to swap it for a 350ohm stator
 
Ah! I see, is it just luck of the draw to get a 350ohm stator or 400+?

Will try getting a cleaner connection in a bit. Thanks.
 
AFAIK, someone got these somewhere near the source of the supply chain thinking they might make a fatter spark - we said 'no thanks' and haven't see one since

I have no idea what the online sellers have now, but haven't seen one come in for testing or repairs since I built the tester and started putting free CDI & magneto test in my ads..
 
the more winds would make more voltage.

unfortunately you then have to design the cdi around the new, higher voltage.

it would run more advanced, simply due to the way the CDI circuit is configured.

if theres no zener diode or similar way to restrict current through the gate of the SCR... youre gunna fry it, no matter what, and then... the main capacitor needs to be up rated to take the extra voltage. exceed rated voltage, and poof... the magical smoke inside escapes! :)

then is the higher voltage coil up to the CURRENT demand? a discharged cap is much like a short circuit...current goes through the roof, while voltage almost hits zero... as it charges, the current decrease and the voltage starts increasing (ohms law, E=IR...) until it reaches a point that it cant take any more charge...or minimum current, at full voltage potential.

by increasing the voltage, the current also increases... as the capacitor and its "resistance" is still the same. i say "resistance" with quotes cus its a bit more complex than that.

the reading you get with an AC meter, or any voltmeter, will be a good approximation, but will NOT be the TRUE voltage. the CDI isnt running at a constant 50/60hz, which is what most AC meters are designed for. they also "usually" only read out RMS voltage, which is an average voltage. the magneto doesnt produce a clean sine wave, but rather a peaked, almost square wave. RMS is only useful with sine waves, at which point its roughly 0.7 of the PEAK voltage. RMS may read, say, 700 volts, but the peaks will fry a standard 1n4009 diode, rated at 1000v...

me, im starting to agree with your pa...bad luck, much? cus i still, personally, have not fried a CDI! (read on)


you may be better off getting a new magneto AND cdi at the same time.

lastly...if you got a 50 volt transformer... or even a straight 1:1 isolation transformer... you can test the cdi with that. (remembering the plug needs to be earthed to the black wire still)

you "could" just plug it into the wall socket, but DONT.


DONT


DONT


DONT DO IT.


you may wake up DEAD.


the current available at a power point is DANGEROUS. still, even the 240 mains here(AU), is only half the voltage that the cdi unit experiences...it just wasnt designed to take a virtually unlimited current dumped into it, with a nice clean sine wave... (low impedance source)

i found that they WILL fry after about 20 seconds running on mains AC... :p even with fat 5W resistors limiting the current...

wanna experiment?


rohmellcdischem.jpg


i take NO credit for this circuit, but it DOES work, you can buy all the necessary components for less than $5, and or...can always find the components in old power supplies etc. you may have to do a few searches on data sheets....say, a c106d works just as well as the BT151 or similar... (the one component with no label!...its called an SCR or silicon controlled rectifier) use 1n4007 or higher if you can get them, not the 4004... and kick cap up to a 600v or even a 1kv type...

or, if you really up to it...

rohmell - ivan H CDI mod 2.jpg

once again, someone elses work, not mine!


note that it includes the "jag CDI" settings,much better value than spending $75 dollars!


slightly more complex. i have a PCB designed for it if interested, measures about 30x50mm.... a lot of work went into getting it that small! and i also did change a few things, not an exact copy. better :)


im currently working on an entirely different take on the idea, using absolutely nothing familiar from these two circuits bar the main capacitor... im waiting for a specific component to drop below $5 EACH, unlike the SCR which can cost 5c in bulk....
 
Wow!! Thanks for that diagram! Yeah I'm starting to agree with the old man as well, I'm going to go ahead and order both a new magneto and CDI in hopes I can find the problem. I guess most vendors sell the same thing? That $5 build seems like a pretty fun project though.
 
You guys aren't going to believe this...

5 days ago after my post I ordered 2 new magnetos and 2 new CDIs from BB
waited for the arrival anxiously, and it just arrived!

So about an hour ago I received my replacement magnetos and CDIs in the mail from BB (along with a bike rack I've been looking to get) and I take the kit out of the box, first thing I see, packaging is ripped, some bags have holes in them, bike rack is bent out of shape... :eek: I'm missing the mounting and nuts and bolts for one of my CDIs. but it gets worse...

Both CDIs are dead, won't read anything on the multi-meter (just sits at 1)
Both magnetos are at exactly 485 ohms...

Is this a freakin joke?! I called BB personally to ask what gives, I was informed that "all CDIs read 1 or 0 on a multimeter unless you cut off the wiring" which can't be correct.

I'm really getting frustrated now. This HAS to be just unlucky me right?

EDIT: I just talked to BB and they said they would email me their address for replacements to be shipped, then they just sent me a blank email. I'm about to start pulling my hair out... Where can I find a working CDI?! Am I the only one in this world with 4 dead units?
 
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go back, check you earths, check everything because there is no way anyone gets more than one dead cdi in a row.

there are only two wires. one is ground, one is "hot".

3 with the plug wire.

between plug and black wire... 2.2-3k, not polarity sensitive. (set to ohms)


between plug wire and blue...diode check reads 1.2v, with red lead of multimeter on plug wire. (set to continuity/diode check)

nothing when black lead of multimeter is on plug wire.

between black and blue, with blue on the red lead...nothing.

with black on the red lead... diode check reads .6v between black and blue.


on the engine itself.

bolt on magneto, after ensuring faces are clean and theres good contact. sandpaper. steel wool. etc.

between black and the HEAD especially...you should get the same reading within an ohm or two, as when you just short the meter.(set to ohms)

or theres continuity. etc etc.


by that token, between blue and any point on the engine should give you the resistance of the magneto coil plus an ohm or two at most.
 
My results for both magnetos and both CDIs:

When I turn on the multi-meter it displays 1 on default

-------------- first CDI

plug to black wires= 1
plug wire to blue wire diode check with red lead on plug wire= 1
black to blue wires, diode check with red lead in blue= .807

-------------- second CDI

plug to black wire= 1
plug to blue wire diode check with red lead in plug = 1
black to blue diode check with red lead on blue = .804

magneto wires = 488ohms
magneto wires = 485ohms

the only reading I seem to be getting on BOTH CDIs is on the black to blue diode check with my red lead on the blue wire. hopefully this can help someone on here isolate the problem. I haven't tested my recently kaput CDIs with a diode check, but I can if needed.
 
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well, i dunno whats going on here, but...disregard what i said with the diode checks etc on that cdi in my last post!

why?

well, it was good last time i used it, but today...after wiping off the cobwebs, it went back into a bike.

one pop and it became my FIRST EVER blown CDI :)


so its readings are definitely suss.
 
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