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Has anyone here had an ignition coil go bad on their KDX? Is this a common problem?

I went riding a couple of weeks ago and noticed towards the end of the day my 220 was getting harder and harder to start. It finally got to the point where the bike simply would not start. I pulled the plug and it looked fine...new plug did nothing. I gorund the plug on the head outside of the bike and couldn't see/hear a spark.

I finally got a chance to trouble-shoot the bike and as far as I can tell it's the coil. The service manual's test for resistance on the secondary coil shows an open circuit.

I guess I am just confused about the way it failed (if infact is really is dead). I would have thought it just would have suddenly died while the bike was running but at no point did it even give me a hint other than being progressively harder to start.

An unusual way for a coil to fail in my experience. Sure that the secondary wire and spark plug cap are intact? (Spark plug caps have a screw type pojection which embeds into the end of the secondary wire. Sometime this will loosen up and not make good contact.)

If I recall a number of people have experienced a failing in the excitor coil feeding the iginition coil.

Check all your ground connections for corrosion and make sure they are making good contact.

You can check the coil (and the high tension lead for that matter) by hooking the coil up to a battery. Connect the ground side, tap the hot side and you should see a good spark (blue) every time your test wire is removed from the + side.

With the cap removed from the wire, you can check the cap separately with a meter.

I don't know what voltage the 'tester' puts out they refer to in the manual, but the spec is a 6mm spark! That's pretty stout. Should have no problem seeing/hearing a spark with good connections (and a properly working coil).

To answer your question specifically: No, the KDX ignition coil is not a common failure item. As IC said, some have had problems with the exciter coil, but not enough for it to be 'common', either. Both of those comments based on what's happened on KDX boards over the past seven years.

The 'progressively harder to start' part IS a symptom of an spark system headed south, though. Whether due to a poor ground, a failing exciter coil, poor high tension connection, OR an ignition coil..any of them can have trouble with voltages generated with kick speed as opposed to running speed.

Good luck.

Let us know what you find out!

Again...an 'open' tested according to the book (cap off) is an easy tell. If that's what you got...it's broke!

Oh..DO be sure you have your meter set to read the K-ohm range your looking for. If you're set to a 1K-ohm range, you WILL read an open on the secondary circuit.

I had the primary side fail on an air-cooled kdx. It was fairly new at the time, and it began to miss, then failed entirely. I still keep a spare coil in the vault.

If you checked the secondary circuit and it doesn't read around 7 K-ohms resistance (or whatever the 220 manual specs) it is indeed the coil that is faulty. Most specs include a 20 percent variance.