A friend of mine just bought a brand new wr400 99 model ex showroom stock and it run fine for two weeks and then started fouling plugs every time he rode it.I gave him a hand with his jetting because his bike is the same as mine and we ride in the same areas and my bike is o.k .Rejetting did not help the problem, then someone said what about the C.D.I so he had the bike shop check it with a multi meter and it checked out fine. Still not happy he swapped the C.D.I with another bike and the bike run great so he had it replace under warranty and his bike hasn't had a problem fouling plugs since.

I never thought this would have been the problem but I rode the bike just before and just after the C.D.I was changed and what a difference.

Not an expert just my 2 cents worth.

Could this be why some of us can't get our bikes to run lean? I have been up and down the range of my DVP and the only thing that works (most of the time) is the top groove. I'm already thinking of who I'm going to talk into a CDI swap/test...

how much is a cdi...

A C.D.I. will run you about 200$ +Tx. You can chk out for parts & prices. They seem to have good prices.

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