Can a CDI be replicated?

[Mr. Peanut]

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]

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]

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]

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]

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]

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]

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 :devil2:

[Ixion]

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

[SwanTiger]

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]

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

[SwanTiger]

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]

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]

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]

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.

[Motu]

A common mod was to remove all the silly ''magneto'' crap,and just use the points in a total loss system - but then you would have a battery.

[Mr. Peanut]

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

The MC28 does, one for the road one for the track. Nigh impossible to derestrict.

The MC21 has different engine maps for each gear with 4th 5th and 6th being retarded to lower top speed. You splice the 3rd gear map to the other three and bingo, full power.

Also uses a throttle position sensor and a control system for the powervalves.

What a headache.

:beer:

[Motu]

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.


If it has a seperate charge coil and triggers it will be CDI,most older 2 strokes were CDI,and '80's Honda's were too,with charge coils in the stator and the trigger in the right case.CDI is used on bikes,specialy 2 strokes,because the intense but very short duration spark will blow off fouling deposits.The short duration of the spark is bad for emissions,so CDI started disapearing sometime ago.

Kawasaki were one of the first to use CDI,and they used the surface gap plug - so when I had my KT250 I tried a surface gap plug (outboards used CDI and surface gap plugs too,we did outboards too,so pocketed a plug).OK,so it started and ran,maybe even ride it - but a normal plug was way better.

[Expert]

I copied this from another site but I know this works as i have often bodged on another cdi unit off a different bike and it's always worked.
Unfortunately the diagrams didn't copy but there is a website address at the bottom so if you're interested you can just go there.
Anybody got a xt200/ag200/trike200 motor they want to sell?


A Simple Motorcycle Electronic Ignition Replacement.

There are many motorcycles which use electronic ignition systems and all have one thing in common, the black box costs a fortune.
For those with small bikes, the costs of replacement can be minimal, as they all have the same basic design. The following simple modification has been run quite happily on Honda NS125, KTM 125 and Yamaha TZR125. All had no electronic ignition systems other than the contents of the generator on the engine. Typical set-up.
Inside the rotor are usually two main coils. One coil is fairly large and supplies about fifteen to thirty volts AC to the rectifier for the battery and lights. The other coil is a smaller, more finely wound coil to supply a hundred or so volts to the CDI unit. Outside, or sometimes inside is a small thumb sized pulser coil, which triggers the CDI at the correct time for the spark.
Remove the rotor and the coil mounting plates. Inspect the wiring to each coil and make a note of the colours to each. Locate the fine wound high voltage coil inside the flywheel generator and inspect the components carefully.
Eventually there will be an earth wire, and a wire or two from the high voltage coil, a wire or two from the heavier coil for the lighting and battery charging, plus a wire or two from the small pulser unit.
In some cases, the small pulser coil and the high voltage coil may not be earthed, so will have two wires each, one from each end of thier coil of copper wire. As these components normally use an earth, then this can be done by extending the wires and terminating them to an earth tag outside the crankcases. If this deos not work, then they are probably connencted inside theorigional CDI unit, but for the C90 unit, they can be earthed.
The larger lighting and battery charging coil may have two outputs, this is usually one for charging the battery and the other for direct lighting. Simply place a headlight to each, to see which is which, once the engine is running. Headlights can work quite happily on AC, so no fancy electronics is needed. For charging the battery, use a single diode. If revving heavily on a regular basis, then a voltage regulator will keep the battery from boiling. If direct lighting keeps blowing, simply fit larger wattage bulbs or add a simple 6 or 12 volt limiter to the headlight circuit. A limiter is a cheap and basic device which simply bleeds off excess voltage, so the bulbs do not blow.
The spark from a C90 ignition will jump the gap in a 50cc to a 1500cc bike, as all spark plugs are essentially the same. There is no need to have a big CDI unit for a big bike. The only time a big CDI unit is needed is for a multi cylinder machine. (If the cost of four C90 set-ups is one tenth the cost of the genuine article, then at least have a try at fitting four sets.)
The electronic ignition of many motorcycles and similar machines with electronic ignition can be run using the cheapest and most easily available electronic ignition in the world. Honda C90 parts are available from all second hand bike dealers and breakers, usually for a few pounds, always try to get the wiring loom as well, or at least the part of the wiring loom between CDI and engine. The parts needed are the CDI unit, the wiring loom connector and a foot or so of attached wire, and the ignition coil.
The simple sand commonly available Honda C90 CDi unit works very well with most small two strokes. Occaisionally, it also works with many fourstrokes which use a mechanical advance and retard unit. To check for a mechanical advance unit, it looks like a set of bob weights restrained by small springs which will fly out when running. This is common on most fourstrokes with points and can also be a conversion for some older machines.
The picture shows that coils are now very small, some not much bigger then your thumb by using much higher primary voltages from the electronics box, they can now be placed in the spark plug cap, and each coil triggered from the electronics individually.
The basic set-up.
Wiring diagrams use a colour code. The normal Japanese set-up uses western nomenclature. BK black. BU blue. R red. Y yellow. W. white.
The Honda C90 CDI unit is very simple and has only five wires.
The earth, the pulser coil input, the high voltage input, the output to the spark plug coil, and the kill switch wire.
To this will be needed a spark plug coil. Look for the CDI mark on the grey plastic coil body. The latest mini coils are also very good, and can be attatched directly to the top of the spark plug, with a little modification. Older points coils are not suitable.
The earth.
Green.
This must connect to the engine casing, and to the frame, so the kill switch will also work.
The pulser coil input.
Blue with yellow tracer.
This simply goes to the pulser coil. The change in magnetic field as the flywheel rotates, causes a small trigger spike of electricity to discharge the big capacitor in the CDI unit into the ignition coil. If the timing is out, then the two wires on the small pulser coil may need to be swapped, so the north-south magnetic pulse is reversed. This allows the trigger to occur at the front or tail end of the pulser strip on the outside of the flywheel. So if your ignition timing is out, swap the pulser wires around.
The high voltage input.
Black with red tracer.
This supplies electricity from the coil inside the flywheel to charge up the big capacitor inside the CDI unit, so it is ready to be discharged by the electronics, upon command from the pulser unit.
The output to the spark plug coil.
Black with yellow tracer.
This discharges the energy in the big capacitor into the high tension coil to the spark plug, changing it from a hundred or so volts up to the 20,000 volts or so to jump the plug gap. The ignition coil must be a CDI type, so buy this at the same time as the C90 CDI unit, so they will work well together.
The kill switch wire.
Black with white tracer.
This simply shorts out the power to earth. In the C90, it simply shorts to earth via the ignition key switch, so the pulse from the flywheel high voltage generator does not charge the capacitor, simply preventing the engine from working.
Also refer to the wiring diagram for the position of the wires if the wiring loom connector is not available.
The diagram includes the checking diagram for the CDI unit. The two probes of a multimeter are placed across the various pin connections, and the appropriate reading is checked.
The measurements are in ohm resistance.
The open ended figure eight on it's side is infinity, so maximum resistance with effectively no connection is required.
SW is the switch , which is the black and white kill-switch wire.
PC is pulser coil.
E. is the earth.
IGN. is the ignition coil
The Diagram.
The big circle is the flywheel stator, with the two main coils.
The thick coil supplies the lights and battery.
The finer coil goes to the black/red wire on the CDI unit.
The small coil on the outside is the pulser and is connected to the blue/yellow CDI wire.
The two measurements beside the ignition coil is the primary and secondary windings.
Primary is connected to the earth and CDI connector tag, and is the low 0.4 ohm resistance.
The secondary has a larger 4,000 ohm resistance and connects to the earth and spark plug thick HT lead, (without the plug cap, which may also contain a resistor).
If the lacquer on the copper coils is damaged, it can be cleaned up and re-lacquered with nail varnish. If the coils are badly broken, they can sometimes be wound back a few turns and rebuilt using more lacquer and wrapping in masking tape. Vinyl tape is not strong enough in the hot engine area. The best wrap is cotton cloth and epoxy resin.
Replace all components ensuring the wires pass through the waterproof seal. If this is missing, then silicone bathroom or gasket sealer is acceptable.
Wire up appropriately as mentioned earlier and check for a spark.
If the engine does not run, check the following.
Disconnect the kill switch wire.
Use a strobe and if the timing is out by twenty or so degrees, then try swapping the pulser coil wires, as the pulse may need to be the other way around North South and vice versa.
If no spark, then swap the high voltage generator wires in the backing plate. This is rare.
Check the wiring is correct.
Check the components are good, using a multimeter.
If all else fails, you have lost just a little cash and some time. The rest is still available for the original and probably expensive genuine CDI unit.
See the home page at www.btinternet.com/~jhpart/index.htm __________________________________________________

[Spyke]

Can other cdi's be used the same as the c90 because i don't think we'd have a heap of them lying around here.

[Ivan]

Most people fall into this trap CDi CDI CDI most likely your bike has a TCI.
Most modern bikes are modern meaning mid 80s on then you have ECU etc.

the internals of a CDI are very basic we had to make one at Polytech and get it to spark and work and it was heaps of fun.

I haveit written down somewere here and will dig out papper work and tell you about the internals.

Now pretty much to your answer can it be transfered from one CDI to another well so long as the internals are the same and work exactly the same then yes but I mean you see alot of guys running Ignition packs of KX125s etc on bucket bikes liek RG50's

Its pretty simple so long as you have a source a trigger and everything matches it should work

[Spyke]

cheers ivan, I'm getting a kt250(1970's) in the next few days and i think i heard the guy say that the cdi or something in the timing was out. which brought me to think if i can change the whole thing it should get rid of that problem.
i'm not really fimiliar with advancing and retarding but he had to retard/advance it fully to get it to run near right.

[dhunt]

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
Very cool site :2thumbsup I've thought about designing an ECU but it hasn't got past the thinking state - hard to get motivated when you play around with micros all day at work. Top effort to the guy for actually making one.

[Motu]

cheers ivan, I'm getting a kt250(1970's) in the next few days and i think i heard the guy say that the cdi or something in the timing was out. which brought me to think if i can change the whole thing it should get rid of that problem.
i'm not really fimiliar with advancing and retarding but he had to retard/advance it fully to get it to run near right.

The KT250 was one of the first bikes with CDI,and were pretty reliable for an early system.But time takes it's toll.If he has to play with the ignition timing then something else is wrong - I had a KT250 for 12 years and always ran it full advance....a new piston and seals and it ran perfectly on standard timing.Go to the KT site,Fred in Wellington makes heaps of KT parts and sells them to the world.

[Spyke]

The KT250 was one of the first bikes with CDI,and were pretty reliable for an early system.But time takes it's toll.If he has to play with the ignition timing then something else is wrong - I had a KT250 for 12 years and always ran it full advance....a new piston and seals and it ran perfectly on standard timing.Go to the KT site,Fred in Wellington makes heaps of KT parts and sells them to the world.


so it may need new piston and rings? can you tell me why on an old piston the bike would need to be advanced?

cheers guys