problems with 450 need help.

[300racer]

I just put a new timein chain in on my 450 and when I got it back together it wouldn't start. so we pulled it and it will pull start and it runs well at high rpm's for a while then it just dies. when I it try to kick start it all it does is backfire every few kicks and it will act like it wants to start if I hold the throttle wide open when I kick it. I know it sounds like a timing problem but it is in time for sure. any suggestions will be greatly appreciated.

[desratt]

did you bang the magnito putting it together

[300racer]

that could be a possibility.

[hondardr4life]

Are you sure its timed right?

[300racer]

I am sure it is timed right I checked it twice my dad checked it once and my friend has even checked it cause thats I thought it not in time.