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1987 CDI

4329 Views 13 Replies 4 Participants Last post by  operose
So my CDI died, All of my numbers check out good on the charging stator and trigger, so I found a used CDI on ebay. I put it on and it is getting a spark but its putting out a spark on every stroke, not just the power stroke, basically a constant spark as the engine turns over. As you can imagine this doesnt work. Any possiblity the trigger is causing this? It checks good on resistance, I cant imagine how it could constantly send a signal. seems like this CDI is bad too, it is a used 87 CDI. anybody?
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They seem to get some extra "pep" when the CDI is about to let out its magic smoke.

Sounds like it is sparking fine... you say it fires and sputters, but won't start?

Don't have any immediate advice, but keep digging. It is probably something small that has been overlooked, happens all the time

"The wasted spark system is an ignition system used with some four-stroke cycle internal combustion engines. In a wasted spark system, the spark plugs fire in pairs even though one is on its compression stroke and one is on its exhaust stroke. The extra spark on the exhaust stroke has no effect and is thus "wasted". This design halves the number of components in a typical ignition system, while the extra spark, against much reduced dielectric resistance, barely impacts on the lifespan of modern ignition components."

That example is for a 2cyl engine, but the principle is the same. The spark plug fires on both power and exhaust stroke, but the firing on exhaust doesn't matter. As long as it is actually firing once at the right time in the stroke and is getting fuel and air, the bike should run (but perhaps poorly depending on other issues...)

Is it literally sparking "constantly" ?? It should not fire on the intake stroke which might be your sputtering issue.

Did you have the rotor off? Are you sure the "pulser coil" (trigger as you call it) checks out spec wise?

Keep feeding us info and we can help you figure this out. Don't get too discouraged
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