[mckenzie80]

I'm in desperate need of help pinpointing what piece is bad that has made me loose fire on my 2005 400ex! 2 weeks ago I rode it ran great parked it and 4 days later went to start it and have no fire to plug. I already tried a new plug nothing! Any help would be greatly appreciated!

 

[retro]

Bad kill switch. Dirty/corroded plug connections in the wiring harness. Bad ground connection from harness to motor/frame. Did you try tapping on the CDI while cranking it over to see if it gets spark then? Beyond those basics you'll need the service manual and a multimeter to check each ignition component.