I have a 2000 400 ex. Runs rough, just replaced piston, rings, stator, and cdi box, still doing the same thing. I noticed the timing is adjusted all the way out. Is this my issue? Do I need a new timing chain?
If you replaced piston and rings you really should have replaced the timing chain and everything associated with a top end build.
Can you confirm the timing is set dead on?
Where did you purchase the CDI and stator from? Are they OEM or known GOOD brands or ebay/Amazon China junk?
They are good parts, and have great compression and great blue spark now. It is still doing the same thing, backfiring, and running rough, won't stay running. I'm hoping it's just the timing chain. Having that put in this weekend