I like to say thanks first. I'm new and read a lot of stuff on this site and it helped.
I have a 04 yfz 450 that I just finished putting back together. the rod went out and I had to replace everything even the case. it has a hot rod stroker crank, Athena big bore kit 98mm piston , port & polished head , kibble white valves & Curtis sparks full exhaust. fires right up and idles fine run good.
so I took it down the road got back let it cool down and there is no oil left in the reservoir it is all in the crank case. the crank case is full of oil if you open the timing mark spot oil starts coming out of it. I have taken the screen out of the bottom of the reservoir and cleaned it already no luck there either. any help please  

found it if you ever take the side cover off make sure that you put the dowel back into the oil pump. it fell out and i did not see it. the case will fill up with oil. hope this helps if anyone else reads it. take your time and make sure that you put all the pcs back in.