Lifan BVH valve clearance??

I am installing a Lifan BVH on a buddies x4r gpx motor. He is also running a big bore kit. The head is on and set. The cam is set properly, and so are the rocker arms. I can set the exhaust lash at .004 with no problems throughout the stroke. The intake stroke is where the problem is. I set it at .004 lash, and when you go through the stroke, the piston will hit the intake valve and stop at a certain point. I am turning it over by hand, so i can feel the piston coming up slowly when it hits. I dont know if there is something I have wrong, such as the cam being backwards. I am pretty sure it is where it needs to be. Has anyone else had this problem. thanks



cory