YZ450F 03 Sparks driving me crazy

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

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

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

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

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

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

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