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03 450EXC no spark, reversed polarity coil exciter pulse

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Working on a late 03 early 04 450EXC with Kokusan 4K3B ignition system for a friend, he bought it and rode about a mile and it quit and never restarted found no spark. After digging into it a little further I found the coil to be defective and way out of range on secondary resistance. Replaced and now have proper resistance and can make it manually fire with a starter button switch and a power source. Now comes the weird part started looking for possible causes and found that the coil does indeed have a primary exciter input pulse, but it is a ground pulse instead of a power pulse. Pulse timing is accurate for TDC and all but has somehow decided to reverse polarity, really weird to me and no one around here has heard of such a thing. Knowing that CDI boxes are common I feel like something must be shorted or contacting inside the CDI, want to be sure before condeming a $221 part for this bike. the CDI has not been relocated yet and the bike is stock without many miles and none are hard miles. Any ideas?

Edited by chop342

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The more reading and research I've done keeps leaning towards the CDI box being defective, sounding like they are much less insulated than others and very susceptible to heat off the radiator. Anyone got any other ideas before I condem a CDI?

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CDI box failed, best i can tell when the ignition coil (which turned up to have hugely over spec resistance both primary and secondary) failed or shorted it must have killed the CDI. Stuck a new one on and relocated to airbox and its perfect.

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well my nemesis bike returned, same situation rode for a while and engine quit and had no spark. A small weak spark is being made on a tester but not enough to jump the plug gap, and again with KTM's amazingly terrible service literature we go testing with only resistance values and this time all components are within specs. I thought i might be missing something so i have several of my friends test everything with the factory manual beside them and they too found everything in spec. so i took the removed components to the KTM dealer and had them check them and they had the same results for us and said "good luck". Had a coil, and pickup coil and CDI laying around from a previous project and neither of them made any difference. Anybody got any other ideas before we just start throwing parts at this thing till it runs again?

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