04 YZ450 ignition problems

3 replies to this topic
  • FLjoyride

Posted May 08, 2007 - 05:32 PM


I recently bought an 04 yz450. As soon as I got it I changed the oil and filter, replaced the stock air filter with a K&N and took it out for a weekend ride. It performed good and I had no problems (except some hard starting on cold mornings). After I got home I changed the oil again and checked it.. it didnt register on the stick (idled it for a good 4 mins). I added a little more and it registered high but in the range. Took it for a 20 min ride and it ran fine. Parked it for a few hours then fired it up again and got about 500 feet before it died. I started it after what seemed like 30 kicks and drove it home where it died again and then wouldnt start. First thing I did was check the oil which was just about coming out of the dip stick hole. Changed the oil again thinking maybe I did something wrong.. still won't run. So I check the spark and sure enough there was none. I went through the testing for the stator coils and the ignition coil. While I did this I found that the wire for the neutral sensor was melted and had broken, so I crimp connected that back together after testing that too. After that all of the tests passed except for the ignition coil. I got a reading of 0.000 Ohms across where the connector goes (supposed to be .08-.1?) So I bought a used coil off Ebay for $30 and tried it.. same problem. Measured that one and got 0.000 Ohms as well. Could I have two bad coils.. a bad CDI box, or a bad meter? I will bring the coils to the local dealer tomorrow to have them check them out but I was wondering if any of you had any suggestions.

  • FLjoyride

Posted May 09, 2007 - 03:04 AM


Could the neutral wire fry the CDI? It had corroded wire around where it was melted so it has been shorted out for some time.

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  • grayracer513

Posted May 09, 2007 - 08:17 AM


In actual use, the neutral switch wire is grounded any time the bike is in neutral, so there is no electrical difference between that and having a short in the middle of the wire, except that the short doesn't occur when it's supposed to.

A shorted neutral lead will lower the rev limit, and alter the ignition timing map, which will make the bike run poorly, but it won't make it miss, an dit certainly won't keep it from running.

  • FLjoyride

Posted May 09, 2007 - 09:19 AM


I'm thinking it's the CDI box.. and that my multi meter doesn't work too good below .5 ohms or so. I will check the connections one more time and go over it real good before I buy a CDI. I hope I didn't buy a lemon.

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