I've been trying to diagnose a weird condition with an 03' yamaha wr450. Has anyone had this happen or have any clues what to look for with this. My buddy raced the bike in a nasty harescramble and overheated it so bad that the bike just died and would not start after this. He went home with it washed it and began to check it out, he found that the wires coming from the pulse rotor and going to the cdi box had cooked right through the insulation. So he fixed this up pretty good and the bike started. Now the bike will run with the revs up but if ya let it drop to an idle it just dies and wil not start up at all unless you put the choke on and then it will do the same thing again. We checked out tha carb. and the hot start unit but this looks good. Could anyone give me some clues to this???? Thanks in advance.

Have you tried checking you TPS sensor. The manual goes through on how to check it. :)

maybe water in the carb, it sounds lean

It is hard to overheat a properly jetted WR450. It has huge radiators that work very well as long as you are moving along in first gear just above stalling the bike should not overheat in hot weather. Your jetting may be on the lean side contributing to the overheating. I like to run on the rich side just off idle to protect the engine in the slow nasty technical terrain conditions.

were the wires cooked due to an electrical problem or just heat from the header or motor? may be the motor is real lean causing it to overheat.

They were not touching anything that could have melted them so I guess it would be from an electrical issue?

I would say your problem is most likely in the CDI unit which controls your spark. When the wires that run into the unit were cooked, It most likely was damaged.I would take it to yamaha and have them do a diagnostic on the unit.

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