Discussing CDI charateristics - Page 6 - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #51 of 56 Old 09-13-2019, 12:34 AM
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The ac is for gen1 or when the magneto coil that feeds de CDI is damage , you can put a d.c feed from battery (for the diagram gen 1 d.c.chinese later i Will post how to conect ..)

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post #52 of 56 Old 09-13-2019, 12:38 AM
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I post a video on you tube called (klr650 con cerebro chino) that is working with the d.c .CDI Chinese ,with the magneto gen2 modificated for that , the photos i upload before
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post #53 of 56 Old 09-13-2019, 12:45 AM
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Damocles i still dont indestand , your question, and for what is the inverter?
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post #54 of 56 Old 09-13-2019, 05:12 AM
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Originally Posted by Alejandro Mercado View Post
Damocles i still dont indestand , your question, and for what is the inverter?
Short answer: The INVERTER converts DC into AC, permitting transforming 12 VDC into maybe, say, 400-600 V AC(or more). The higher-voltage AC is rectified, charges a capacitor, then . . . the capacitor is discharged through the ignition coil's primary windings, the consequent pulse transformed to an even higher voltage through the ignition coil's secondary windings, causing a spark.

Long answer (courtesy WikipediA):

-----------------------

AC-CDI
The AC-CDI module obtains its electricity source solely from the alternating current produced by the alternator. [As in Generation 1 KLR650s] The AC-CDI system is the most basic CDI system which is widely used in small engines.

Note that not all small engine ignition systems are CDI. Some engines like older Briggs and Stratton use magneto ignition. [There we have it; "magneto ignition," an arrangement I tried (unsuccessfully) to reference in a previous discussion with another poster.] The entire ignition system, coil and points, are under the magnetized flywheel. [Note: Just incidentally, a "magneto ignition" uses coil and points.]

Another sort of ignition system commonly used on small off-road motorcycles in the 1960s and 1970s was called Energy Transfer. A coil under the flywheel generated a strong DC current pulse as the flywheel magnet moved over it. This DC current flowed through a wire to an ignition coil mounted outside of the engine. The points sometimes were under the flywheel for two-stroke engines, and commonly on the camshaft for four-stroke engines. This system worked like all Kettering (points/coil) ignition systems... the opening points trigger the collapse of the magnetic field in the ignition coil, producing a high voltage pulse which flows through the spark plug wire to the spark plug.

If the engine was rotated while examining the wave-form output of the coil with an oscilloscope, it would appear to be AC. Since the charge-time of the coil corresponds to much less than a full revolution of the crank, the coil really 'sees' only DC current for charging the external ignition coil.

Some electronic ignition systems exist that are not CDI. [As in, Generation 2 KLR650s.] These systems use a transistor to switch the charging current to the coil off and on at the appropriate times. This eliminated the problem of burned and worn points, and provided a hotter spark because of the faster voltage rise and collapse time in the ignition coil.

DC-CDI
The DC-CDI module is powered by the battery, and therefore an additional DC/AC inverter circuit is included in the CDI module to raise the 12 V DC to 400-600 V DC, making the CDI module slightly larger. [NOT the case for Generation 2 KLR650s; the model has no stinkin' CDI whatsoever.] However, vehicles that use DC-CDI systems have more precise ignition timing and the engine can be started more easily when cold.

-------------------------------

Summary (in the general context of engines, as on motorcycles):

AC-CDIs are powered by alternating current from the engine's fundamental electric power system. [Think alternator, stator.]

DC-CDIs are powered by low-voltage DC [As in, rectified, regulated 12 VDC], but must have an inverter in the circuit to convert the DC to AC for high voltage step-up; consequent higher-voltage rectified and used to charge a capacitor.

MAGNETO IGNITIONS [As the phrase is commonly used in Ignitioniana] have no CDI whatsoever, rather, consist of inductive discharge systems with contact points.

Now, WikipediA, and I, HAVE SPOKEN!

“You better put down that gun. You got two ways to go, put it down or use it. Even if you tie me, you’re gonna be dead.” "John Russell" (Paul Newman), Hombre
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post #55 of 56 Old 09-15-2019, 02:48 AM
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Thanks for the story, i know ,what is, but , i dont understan for what can you aplicate on this? Or better question, what is that u want to do, or whats on you mind working???
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post #56 of 56 Old 09-15-2019, 03:40 AM
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Originally Posted by Alejandro Mercado View Post
Or better question, what is that u want to do, or whats on you mind working???
Nothing whatever, Alejandro!

I was just wondering about the application of aftermarket CDIs, whether DC or AC, whether applied to Generation 1s or Generation 2s . . . trying to reconcile the many differences between the respective components (as in, pickup coil, rotor (involving timing lump), ignition coil, etc. And, wondering about the performance consequences, should non-optimum components become orchestrated into any CDI transplant . . . maybe, how AC was connected to an AC CDI from a Generation 2 stator (parallel to the rectifier/regulator input circuitry?). . . perhaps . . . what does the spark advance curve look like from the aftermarket CDIs . . . etc.

Is mentioned in previous posts, I wondered at the difference in size between AC- and DC-powered CDIs; assuming (as stated) the DC versions requirement for an inverter resulted in a larger package than the AC's.

So, back to your question . . . just idle speculation and postulation!

Congratulations on your own successful incorporation of aftermarket (Chinese-manufactured) CDIs!

“You better put down that gun. You got two ways to go, put it down or use it. Even if you tie me, you’re gonna be dead.” "John Russell" (Paul Newman), Hombre

Last edited by Damocles; 09-15-2019 at 03:45 AM.
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