Hello I recently put a new cam chain in my 03 z400 after I got everything put back together it started up and ran great no smoke after about 15 minutes of running it starts losing power,smoking and blowing oil into the air box can anyone help me?  

I may have the answer to my problem. I used ask the experts.com and they seem to think that the oil return line is plugged or air locked. I haven't had time to see yet. I'll keep you posted but hopefully that's it I wanna go riding.