CDI box question

[KDXrider1989]

This might sound like a dumb question, but if the CDI box is smashed up, could it affect spark? It's on the KTM I recently got ( I know what some of you are thinking ) It still has spark, but barely any, I can put my fingers at the spark plug tip and when I kick the engine over it only shocks me a tiny bit, I can still hold onto it. Im not too familiar with how the electronics on my bike work, only the very basic stuff

[bufftester]

FIrst off, who told you to hold the plug tip while you kick your bike over? Probably the same guy that wants to shoot you with his taser

Yes if its smashed it can affect spark, the CDI (which is basically a fancy capacitor) unit generates the trigger pulse for the coil, and damage to it will directly affect spark.

[KDXrider1989]

Lol, it had a tiny bit of spark so I wanted to see if it even had enough to shock my hand, and it barely did. And thanks, I guess I'll have to switch it out then, the plastic on the outside is beaten up as if its been hit pretty hard

[cragwl]

I've been known to make toast while taking a bath. Mmmm, I love toast.

I live by the rule, "if I smashed it, it's broke".

[Roadhazardguy]

Well you know if you can't fix it with a hammer... you have an electrical problem.

[KDXrider1989]

ha! dumb question, i know now im having trouble trying to find a good one. none on ebay, from '98 to '02 they share the same cdi, same part numbers. I'm only finding cdi's from '03 and up

[KDXrider1989]

I just found out that the stroke on the older engines and the newer engines are the same, so does that mean that the newer cdi could work on my bike? the connectors to the cdi are the same on both models also

[Roadhazardguy]

I think that pretty much any CDI could work if you know what wires do what. Stroke has nothing to do with it.

[bufftester]

The short answer is ...maybe...

2 stroke CDI operates exactly like the old points/condenser system, and is based entirely on crank rotation, so stroke, bore, etc have nothing to do with it. Just because the part # changed in a model year doesn't mean the part actually did (plenty of examples on our own Kawi's to back that up). If you're going from say a 1999 250 SX to a 2003 250 SX and the part numbers are different, but the connectors are the same, likely the CDI will work. You could further verify by looking at the wiring diagrams for both years and matching up the wires to the CDI (most have 5 leads, ground, kill switch, primary trigger, and exciter /trigger). Of course the only way to know for sure would be to hook it up and try. You can't damage your motor, at worst it just won't run. In theory you could take a CDI from just about any similar 2 stroke bike from the same year group and use it (most of the CDI units are all built by the same company anyways). The only reason its in that big black box is to hide it from prying eyes since the manufacturers know there's about $3 worth of parts in that $150 OEM part and they don't want anyone taking that away. If it were me and I found one that wasn't too much I'd give it a try.

[KDXrider1989]

thanks guys, much kudos to y'all for answering the questions I had in mind

bufftester, i looked over the newer model cdi and the connections look exactly the same as the older cdi, only it mounts differently to the frame. I guess i could give it a shot? in that case, i guess i could also try a 125cc cdi

[ICRage42]

Had this problem myself with a four stroke china 4 wheeler. SunL look on google and youll see the excellent service and parts they have.

Guess I kinda learned the ins and outs of finding parts compatible because theres literally no parts to order unless you buy someone elses old wreck or swap used in.

CDI's

For the most part make sure its for a 2 stroke or 4. Sometimes you can cheat a bit. I did get a 2 stroke to run in the wheeler but it ran like crap. You already did that with matching a 2 stroke with 2 stroke.

Next the biggest thing is make sure the bike is wired the same. Is the bike your looking at have a battery? So does yours? What Im getting at is there is a difference in cdi design in this aspect. Like the kdx it has no battery and runs off stator ......ok. If I had another the same year kdx but it had a battery to help spark .....the cdi from my first kdx would NOT work . When ordering you would see a difference in cdi design theres usually only two wires switched around. I do believe from memory in my situation the positive and ground. General rule of thumb is if you start the bike and remove the positive wire and it still runs you need this type of cdi if it stops running you need the other. My 95 kdx would follow the remove the positive wire from battery and still runs or remove battery all together.

DO NOT PUT THE WRONG ONE IN YOU WILL DAMAGE STATOR!

I completely fubared my stator on wheeler this way. Found a cdi that looked the same and from same model but it had a different wiring and no info to find this out. It sent a charge back through I guess. So if one wire is switched on your cdi triple check..... if it looks the same coming out of box and same color coding you can feel safe about swapping.

I have little to no knowledge of KTM. But most parts transfer pretty easily and cdi is one of them. Dirtbikes usually are only wired one way (2 strokes anyways).

As Bufftester stated the cdi is nothing more then on/off triggers. Theres just about 4 companies that make them most difference being outside shell design and mount locations. Yes theres about 40 dollars worth of parts but what I was told when contacting a manufacturer is the casing is the most costly part. It is to stop condensation and protection usually in either a pressed aluminum or encased in a resin mold. Never tore into one and was advised not to because there is some capacitors in there and could cause shock if cutting through it.

The 125 will work if like I said above if it is the same setup as yours it will work. If it requires a battery (pull positive off and if is stops running) and yours doesnt IT WILL NOT WORK AND POSSIBLE STATOR DAMAGE! If you pull the positive wire off and it remains running then battery just gets charged maybe to run a light.

If I was a bettin man Id say 88-06 or so cdi would work in any kdx. Its just a basic set of instructions like bios on your computer. It all comes down to how the bike is wired.

I found a new but used stator. Found a new 2006 honda high spark cdi and installed it. Made sure I didnt get the cdi for the rancher or whatever that came with battery , wires were switched. 12mph increased speed and removed the factory rev limiter. Easily pulled front up with ease now. Its a 2000 honda china clone.

So with this knowledge dont steal your kids 125 cdi for too long it should work. Theres no reported gains or losses in performance from putting a 200 cdi into a 125 or vice versa. However a 200 might have the appearance to be bulkier and that was also explained to me that with higher speeds they make them larger to absorb more shock and possible damage.

There is some debate about the size of the capacitor being for the appropriate size bike. Ive heard both sides and really seen no tangible proof and when talking with manufacturer rep he explained there isnt a significant difference other then it probably wouldnt be a good idea to put a 500 cdi into an 80. Try to keep it close as possible. I would go with your first choice. Also like Bufftester said just because part numbers are different doesnt mean its not the same part. Part numbers are an ever changing system. At some point new gets added and part numbers change a bit. Doesnt necessarily mean its not still the same part.

Hope this helps!

[bufftester]

I would agree with most of that other than damaging the stator. The exciter coil is just that, a coil...wire wrapped around some plates. sending voltage through it isn't going to hurt it, in fact voltage travels both directions through it while it's running. Even with a wire in the wrong place, the only thing that will happen is it wont run. Best bet is to keep with same model type for best results as there was some work done with digital CDIs capable of retarding trigger timing, but most of that never made it to production.

[KDXrider1989]

crap, I recently ordered a wire harness and cdi for my ttr 125. Mine has kickstart and electric start with a battery (HAD a battery), the one I ordered is for a kickstart-only model

part numbers are the same though? I guess its only harmful if i had it the other way around

[KDXrider1989]

and thanks ICRage42, lots of help in your post!

as far as the KTM goes, it's a 2000 sx 250, no battery needed, it runs off of the stator. Im looking at an '04 sx 250 cdi, where that bike does not need a battery either. and the connectors look the same, I needa double check. and if they are, then I should be good?

[bufftester]

should be...I looked at the wiring diagrams for both the '00 250SX and the '04 250SX and the CDI is wired the same, same wires, same colors, same plug. My guess is that the part number probably changed because they changed the outer case a little for mounting purposes (haven't verified that though).

As far as the TT-R125 vs. TT-R125LE they use the same CDI, battery doesn't make any difference as it's not part of the ignition circuit, solely there to turn the starter motor and be charged by the lighting circuit.

Let us know how it all turns out...and keep your fingers off the plug on a good CDI....or have someone film it so we can watch

[KDXrider1989]

should be...I looked at the wiring diagrams for both the '00 250SX and the '04 250SX and the CDI is wired the same, same wires, same colors, same plug. My guess is that the part number probably changed because they changed the outer case a little for mounting purposes (haven't verified that though).

As far as the TT-R125 vs. TT-R125LE they use the same CDI, battery doesn't make any difference as it's not part of the ignition circuit, solely there to turn the starter motor and be charged by the lighting circuit.

Let us know how it all turns out...and keep your fingers off the plug on a good CDI....or have someone film it so we can watch

whew, thats very good news to hear for the TTR and the KTM, thanks!

And I'll keep that in mind whenever it comes in, I've been shocked multiple times from a spark plug on accident, no bueno

[KarlP]

If they are wired the same and have the same connectors, the '04 CDI will work on the '00, for sure. KTM does make mapping changes to the CDI over the years and for different CC bikes. Many folks claim a CDI unit from a 125SX is the bomb on a 200XC.
I doubt you'll be worried about that though. A running bike with a slightly different RPM/advance curve (maybe) is way better than a non-running bike.

If you can bear to put up with all the nonsence and have time to kill, KTMTalk will shed more light on it.

[Roadhazardguy]

Yeah KTM talk is a good place. The owner Byron Forbes is actually the original owner of my KDX I found out, real nice guy too.

[KDXrider1989]

I guess a kx125 cdi would be an upgrade for our kdx?

[KarlP]

I guess a kx125 cdi would be an upgrade for our kdx?

I don't know. You can try.

There was a guy on here a few years ago that was making and selling an aftermarket CDI unit for the KDX. He offered a couple of different options, as I recall.