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2002 YZ125 Secondary Ignition Coil Issue

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I have been having an issue with my Ignition Coil on my 2002 YZ125. Let me explain the story of how it happened. Let me preface this by saying I know what is happening and I know what the specific problem is, I need to know if their is a way around this, and if anyone else has had this issue.

So I go for a ride, everything works fine, end of the ride, go to wash the bike. Go to start it up afterwards, it does not rev out, as in it will idle but if you turn the throttle, the ignition doesnt advance, rpm stays same, but the system introduces more fuel and air obviously since throttle is open. This issue started about 6 months ago, so since then I have eliminated all the obvious and went through everything to determine it is in fact the secondary ignition coil that is failing. I am pretty proficient with this stuff and pretty much figured out the problem, but have never seen a topic on something like this and want to resolve the issue permanently.

But I will walk through all the steps to ensure readers that it is this specific problem to save us both time haha. At the time i did not notice the ignition was not advancing and I naturally thought to look at carb, spark plug, plug cap, powervalve, top end, clocked jets, paper towels in airbox ect.....   Well instead of even having to go through the carb, I was actually going to put a different carb on that night either way (Lectron Carburator), and that obviously didn't change anything. Checked Powervalves, changed spark plug, put different fuel in for the heck of it. Checked compression and also looked at the bottom end seals and made sure I did not have an air leak. Everything was perfect, as iv went through the entire engine a few months before this.                 So then I started looking into electrical. First thing I did was replace spark plug cap. That didnt do it, even though that was giving me wonky Ohms readings. Then I went through the entire electrical system, stator, ignition coil, kill switch. Everything tested good except for the ignition coil initially. Ended up replacing ignition coil. I also filed down the frame leads to bare metal that the ignition coil attaches too.  ----- That fixed the problem, or so i thought. Started up and revved fine. Next week, I wash the bike, and it fails again. But this time I let the bike dry out... try a few hours later, and the problem is fixed again. At this point I determined that the water was causing the problem. So I go back and check both igniton coils and realize they both test the same, and that its really hard to get a steady reading on either of those parts. Throw the old one back in real quick and that works fine. Went through and checked all the wires again and used di-electric grease this time on things.

Kept having this problem occasionally since then. It is never the end of the world because I know what is happening...  and if I wait an hour, sometimes it takes a few, it will resolve itself. So the problem: Something going to the secondary ignition coil, or the coil itself is shorting or intermittently failing, and it is because of water. I do a very good job washing my bike and it always looks showroom condition, so I am spraying water everywhere, but all the electric is sealed up. I know a solution would to be not wash it as well or spray up under the tank where electric is, but that is not an option, I would like to resolve this issue.

Thanks for the help

-Kirk

 

IMG_2567(2).JPG

Edited by KirktheDirtEater

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*****Also, have put many hours on the bike since then and have rebuilt and gone through many things since then. This happened last night again after washing, and would not resolve itself until like 3 hours later. It has not happened yet but I am afraid I will jump into a river during one of my races and I will experience this issue. Hasn't happened yet even after lots of muddy rides and races and lots of creek riding.

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Cool looking bike.

When you say second coil you are referring to the manual section II page 78? 

source coil 2 resistance

(Green/White-Black/Red)

44~66 Ω at 20°C (68°F)

If everything else is checking out, the CDI box is not easy to test if at all. Have you tried a different one? Possible hairline crack, allowing moisture to penetrate box. 

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1 hour ago, 2 STROKE YZ DOC said:

Cool looking bike.

When you say second coil you are referring to the manual section II page 78? 

source coil 2 resistance

(Green/White-Black/Red)

44~66 Ω at 20°C (68°F)

If everything else is checking out, the CDI box is not easy to test if at all. Have you tried a different one? Possible hairline crack, allowing moisture to penetrate box. 

Thanks for the reply. Yeah that is what I am referring to. From everything I could figure out through research, the cdi is usually erratic constantly or fails completely, so I doubted that was the problem, and I could not find reasonable priced one to test it against.... Although I did not consider a hairline crack in the cdi though. The reason I suspect the secondary part of the ignition coil is because it will idle, and has a low rpm ignition range (which is the function of the primary ignition coil), but will not rev out which is the function of the secondary ignition coil. That is why i did not suspect it to be CDI since the problem so closely aligns with the function of the ignition coil. 

But I will check for hairline fracture in CDI regardless since that is only thing I have not done. 

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