YZ450F 03 Sparks driving me crazy

Yamaha YZ450F 2003

5 replies to this topic
  • SirAttard

Posted May 26, 2016 - 03:17 PM


Hello there,

I know there is countless treath about this issue all over the internet, but I still can't find one that fix my problem. I hope somoone out there may help me fix my issue.


I bought a Yz450f 03 that died last summer. The precedent owner didn't wanted to spend time on hit and chosed to sell i as it was.


So far, I changed the stator, the killswitch, the CDI unit, I tried the ignition coil of a Yfz450 that seems to be the same, I cleened the neutral switch and I just changed the harness. Still no luck. 


I get small yellowish spark when hitting the kill switch and kicking the bike. These are enough to give me some explosion but I can't start the bike this way. If I keep kicking the engine while pushing the kill switch I have a spark about 1 kick out of 2. 


If it may help, I before noticing the sparl problem, cleaned the carburetor and checked valve clearence. 


I'm sorry if I made any of this unclear, I only speak english as a second language. 

Thanks for your help.

Edited by SirAttard, May 26, 2016 - 04:12 PM.

  • grayracer513

Posted May 27, 2016 - 06:43 AM


Please explain why you would be pushing the kill switch while trying to start the bike.

  • SirAttard

Posted May 28, 2016 - 10:43 AM


It's not that I want to start the bike this way, but it is the only way I get fire.

I think the flywheel don't trigger the capacitor/pick up coil. Hitting the kill switch grounds it somehow and i get some weak waste spark.

Edited by SirAttard, May 28, 2016 - 10:44 AM.

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  • grayracer513

Posted May 29, 2016 - 06:11 AM


What happens if you disconnect the kill switch?  Sounds to me as if you have a wiring fault somewhere.

  • SirAttard

Posted May 29, 2016 - 07:14 AM


Disconnecting the kill switch won't change it. I think I found the problem. I bought a proper multimeter and both stator are nuts.

  • SirAttard

Posted June 10, 2016 - 06:24 PM


Just a little update about this.

It was the flywheel. Seems like it wasn't triggering the pickup coil.

Funny enough, I rode it for about 15 minutes today and then broke the woodruff keeping the flywheel in place on the crankshaft!

Anyway, thanks for the help guys

Edited by SirAttard, June 10, 2016 - 06:31 PM.

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