KDXRIDER.NET

So, my exciter coil failed on me. Now I'm trying to figure out why that happened.



(Old one is the one on the bottom if it's not obvious)

The latest symptoms were that it went from very intermittent spark to no spark at all.

With a new job this summer, and life getting in the way, it took me forever to begin diagnosing it. Finally I got my trusty fluke out and measured the exciter coil winding resistance and got 197 ohms. It should be between 250 and 370. Bingo. The lower than specified resistance means that the coil is shorted. The new coil I got measured around 300 by the way.

Well... I didn't want to splurge a couple hundred on a new OEM one so I waited till one popped up on ebay. Found a whole electrical system off a 2002 for about $130 shipped. Now i have a spare CDI and regulator.

As soon as had the new exciter coil installed, and the magneto and cover on I checked for spark. Nice fat spark. Good sign.

Put the tank on, turned on the gas and she fired up on the third kick!

So, I'm happy needless to say.

Now as to how, or why, this happened? When I first got the bike it ran, but seemed to want to die when it got hot. I thought it was the rings, and since it was a new to me bike I went ahead and replaced them. After that, as stated earlier, I could barely get the bike to run and eventually I couldn't get it to run at all.

When I first got the bike I also noticed the exciter coil wires that connect with the harness were routed wrong and were touching the pipe, which caused the protective cover to melt a little on two of the wires but they never were exposed. Could this have lead to its slow demise over time?

Sorry about the long winded post, I just would like to find out if there's anything I can do to avoid this from happening or if it's just one of those things that just happen over time.

Thanks for reading.

honestly you must of had a wire touching metal or touched together at some time perhaps by muffler.....I would double check your wiring to make sure nothing is grounding out. Other then that it should last you a long time if it was grounding out for a while I could see this happening.

If you want to see stator failures, buy a KTM 50. My buddy takes 2 extra stators with him to every race. He was headed to the line last sunday, and no spark. Ran 10 minutes before. Change the stator and go. He calls them "KABOOMS." But the CDIs and coils last forever...

Stator failures are rare on most bikes, but they happen. The symptoms are like what you had, runs poorly when hot, kind of like a plug that is fouling. The rings are just the opposite, they work better when warm. I can only speculate that if you had no wiring fault to burn it up, there was a weak spot in the coating on the wiring in the stator, and the wiring somehow became damaged electrically from that over time. It is the same with a CDI box, no moving parts, but sometimes they fail. I have had around 30 bikes, and been around friends with them, and can only recall one stator failure and one CDI failure from all those bikes (Ktm 50s excluded). I did see two other stators that failed from "drowning", but it wasn't the stator's fault.

+1 with gsa102. No moving parts, but the exciter coil is subject to a lot of electromagnetic stress. Likely there was a break somewhere in the insulation of the windings that broke down over time. Doubt that the heat from the pipe contributed to the issue, especially if the wire was never exposed, you just got to be the 1 guy in a million that has a stator failure.