Can a CDI be replicated?

**Mr. Peanut** · 19th June 2006, 18:40

Had to buy a second hand one for my MC21. What I want to know is if the data can be loaded on to a custom CDI of some sort.

I was lucky, I only paid 150. CDI's for the MC21 are as rare as a very rare thing.

**oldguy** · 19th June 2006, 21:23

I,m trying to locate a CDI for a 83 KDX175 don't think there is anyway to test if they work or not,

**Ixion** · 19th June 2006, 21:54

This interests me. Can someone in the know explain exactly what a CDI ignition module comprises. I understand the capacitor discharge bit, and the circuit diagram for the one on the Titan seems to imply that is all there is. But some bikes there seems to be much more , a lot of computer logic incorporated. What , exactly?

And how interchangeable are they. In the old days with points , condensor and coils, so long as the bits physically fitted they were good to go. But what about CDI units? In theory , they should be also, after all it is just a capacitor charging and then discharging when a pulse signal is detected.

**Pixie** · 20th June 2006, 11:11

Originally Posted by Ixion

This interests me. Can someone in the know explain exactly what a CDI ignition module comprises. I understand the capacitor discharge bit, and the circuit diagram for the one on the Titan seems to imply that is all there is. But some bikes there seems to be much more , a lot of computer logic incorporated. What , exactly?

And how interchangeable are they. In the old days with points , condensor and coils, so long as the bits physically fitted they were good to go. But what about CDI units? In theory , they should be also, after all it is just a capacitor charging and then discharging when a pulse signal is detected.

Most "CDI's" aren't.
Suzuki refer to many (most?) of their ignitions as transistorised.
And they are just simple current switches to the coil,solid state points in essence.
In modern bikes the ECU controls the triggering of the ignition module and effects timing adjustments (advance).
True CDI's often generate a spark of too short duration.

**Motu** · 20th June 2006, 11:22

You used to be able to make your own CDI igntions...maybe a look at Smith the Dick or Jacar and see what they have.Modern ones probably have a chip,but geeks can get those by the bucket load for 30 cents...Get the resin out and have a look,maybe a simple compomnent has crapped out.Black boxes are black boxes to me....

A quick check shows they have no ignition systems listed....but I remember them being a common kit.You need something to charge the capacitor,and something to trigger it,and they are usualy on the bike...don't know how you would retro those bits.But you should be able to reverse engineer one on the bench easy enough...

**Paul in NZ** · 20th June 2006, 11:31

I'd drop this guy an email. He is a nice guy and if anyone will know - he will.

http://www.cajinnovations.com/MyECU/index.htm

**Ixion** · 20th June 2006, 12:19

Yes, Mr Pixie is correct. i've researched a bit more. What we call CDI units are actually TCI - transistor controlled ignition. Maybe new bikes with ECUs are real CDI, dunno, but they're a different kettle of fish anyway.

One's I'm thinking of are simple.

Attachment shows internal schematic of the Titan CDI. Looks simple enough. Mind you, that's for a two stroke. One for a four stroke probably have several dozen extra parts

**Ixion** · 20th June 2006, 12:21

Doesn't the NSR250 have some sort of credit card gadget that actually holds the engine control data ?

**SwanTiger** · 20th June 2006, 13:42

Interesting thread.

Is someone able to explain briefly to me what is involved in a bike running at a "Total Loss". My bucket operates this way and I would like to know the principle of what is happening. I've got the workshop manual too, so once I've got a grasp I might go have a tu-tu.

I use to dislike 2-strokes but I've been having a love affair with my A 100 of late.

**Motu** · 20th June 2006, 13:46

Battery powered with no charging system - the battery is draining as you ride.

**SwanTiger** · 20th June 2006, 14:22

Originally Posted by Motu

Battery powered with no charging system - the battery is draining as you ride.

Hmm that doesn't sound right as I don't have a battery in the bike. So how does that work is the terminology "Total Loss" incorrectly describing how my bike finds ignition?

The only thing left, that I can find, is a coil tucked away inside the upper part of the frame near the head.

**Motu** · 20th June 2006, 14:25

Originally Posted by Motu

Battery powered with no charging system - the battery is draining as you ride.

That is a total loss system,if you don't have a battery without a charging system you better change the name,because then it's not total loss.

**Ixion** · 20th June 2006, 14:26

This is an A100? If so it probably has a flywheel magneto. No charging circuit (been ripped off).Common on small bikes, scooters etc

Magneto doesn't need battery - may need a big capacitor to smooth things out.

Total loss is as Mr Motu siad. normal bike electrics, with the generator/alternator removed, so the battery is discharging all the time. lasts long enough for one race.

**SwanTiger** · 20th June 2006, 14:37

Ah, learn something every day, thank you for the clarrification.

Yes it does have a fly-wheel magneto.

I knew that, but was told by someone I knew that it was "running at a total loss" so I presumed that to be true. Now I'll go see if I can break it and put it back togeather.