Electrical problem on an '03

Help. Tried to go riding today and bike wouldn't start. I thought I fouled a plug. OK Put a new one in, bike started right up.

Did 2 laps on the track and bike starts missing terribly, not backfiring just misfiring completely. Barely made it off the track under it's own power. In fact stalled for the last time just as I was pulling into the pits. Won't restart.

I pull the brand new plug and it's gas fouled really bad. Stick another new one in the cap and check for spark. NOTHING NANDA ZIP ZILCH!

How common is it for the coil/plug cap to go bad? It seemed to show up when the bike got hot.

I think whatever it was, has been going bad for a while. Last few times I've ridden I noticed a hiccup everytime I'd crack the throttle. It finally died.:thumbsup:

Any advice?

I would throughly clean the carb first. Remove and clean all the jets, float, etc...trash and/or build up may be culprit

TPS also may have moved if it is loose - on the carb

If none of this - possibly CDI

I'll check the carb while I have the plastic off, but it definitely doesn't have any spark.

I'll check the carb while I have the plastic off, but it definitely doesn't have any spark.

no spark - is not the carb.

Are there any common ignition parts that go bad on these bikes? I'm hoping for just a coil. I can deal with $70+ at the dealership. It's going to suck if it's the CDI.

had the CDI go on my 04, thought it was the coil at first since my ohm meter doesnt measure really low resistance well.. I would get a nice meter and check your ignition coil, stator coils, and wiring. then go for the CDI. I got a new CDI for $80 off ebay, seems to be fine so far and I get another 500 RPMs before it redlines.. not that I need it but it was cheaper than OEM. If it turns out to be the coil I've got two now so PM me if you need one.

I had 2 ignition coils go bad on me with in 2 years on my 03 WR450.

I suspect it was overzealous pressure washing on my part.

Ok guys,

Now that the bike has been sitting in the garage for 2 days, I've have a weak spark. Which happened on Sunday too. After replacing the plug for the first time, the bike ran rough. Seemed to load up. I didn't think much about it at the time. I pulled in for a break and it sat for about 25 minutes. It fired right up after that, ran for about 10 mins and that's when it started cutting out really bad. It seems to be a heat related issue.

I've checked all electrical connections (ignition coil, stator coils and kill switch) they are within spec.

Which component is most affected by heat? Will work when cold, will die when hot?

Isn't it so much fun tracking down electrical gremlins?:thumbsup:

It seriously sounds like your coil to me.

When my first one went bad, the Yamaha mechanic troubleshooted my bike for 7 hours before he finally gave up and just started swapping parts. The coil gave him a good ohms reading, but it was bad, none the less.

BTW, the mechanic was well qualified and highly spoken of by people who did not work at the shop.

I just got done going through the same trouble shooting.

It turned out to be the CDI, I tried 3 different coils, a new wiring harness 9had a spare) and finally swapped out the coil.

Sparks came back strong, could be anything.

Coils are pretty robust, just a bunch of wire wrapped around a steel post really.

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